Finding the tenth derivative












15












$begingroup$


I came across this Question where i have to find $$f^{(10)}$$ for the following function at $x = 0$
$$f(x) = e^xsin x$$



I tried differentiating a few times to get a pattern but didn’t get one, can someone provide the solution.










share|cite|improve this question











$endgroup$

















    15












    $begingroup$


    I came across this Question where i have to find $$f^{(10)}$$ for the following function at $x = 0$
    $$f(x) = e^xsin x$$



    I tried differentiating a few times to get a pattern but didn’t get one, can someone provide the solution.










    share|cite|improve this question











    $endgroup$















      15












      15








      15


      4



      $begingroup$


      I came across this Question where i have to find $$f^{(10)}$$ for the following function at $x = 0$
      $$f(x) = e^xsin x$$



      I tried differentiating a few times to get a pattern but didn’t get one, can someone provide the solution.










      share|cite|improve this question











      $endgroup$




      I came across this Question where i have to find $$f^{(10)}$$ for the following function at $x = 0$
      $$f(x) = e^xsin x$$



      I tried differentiating a few times to get a pattern but didn’t get one, can someone provide the solution.







      calculus






      share|cite|improve this question















      share|cite|improve this question













      share|cite|improve this question




      share|cite|improve this question








      edited 9 hours ago









      Shalop

      9,21411030




      9,21411030










      asked 21 hours ago









      user601297user601297

      3509




      3509






















          9 Answers
          9






          active

          oldest

          votes


















          26












          $begingroup$

          Hint:



          $$f(x)=e^xsin x$$
          $$f'(x)=e^x(sin x +cos x)$$
          $$f''(x)=e^x(sin x+cos x)+e^x(cos x -sin x)=2e^x(cos x)$$
          $$f'''(x)=e^x(2cos x)-e^x(2sin x)=2e^x(cos x-sin x)$$
          $$f^{IV}(x)=2e^x(cos x-sin x)-2e^x(cos x+sin x)=-4e^x(sin x)=-4f(x)$$






          share|cite|improve this answer











          $endgroup$









          • 10




            $begingroup$
            First time to see roman numerals to denote derivatives. Nice!
            $endgroup$
            – Taladris
            19 hours ago






          • 13




            $begingroup$
            Lower case too, awful notation if you ask me.
            $endgroup$
            – marshal craft
            13 hours ago






          • 4




            $begingroup$
            I have no problem with lowercase roman numerals in general, but here it looks like taking the power to the imaginary unit (times $v$)...
            $endgroup$
            – ilkkachu
            9 hours ago








          • 14




            $begingroup$
            There will be some confusion when you get to the tenth derivative......
            $endgroup$
            – Spencer
            7 hours ago






          • 5




            $begingroup$
            @Shufflepants en.wikipedia.org/wiki/Fractional_calculus
            $endgroup$
            – BPP
            4 hours ago



















          50












          $begingroup$

          Hint:



          As $;mathrm e^xsin x=operatorname{Im}bigl(mathrm e^{(1+i)x}bigr)$, you have to find first the real and imaginary parts of $(1+i)^{10}$.






          share|cite|improve this answer









          $endgroup$









          • 12




            $begingroup$
            This is by far the most efficient solution.
            $endgroup$
            – Yves Daoust
            21 hours ago






          • 8




            $begingroup$
            Knowing $(1+i)^2=2i$ helps too
            $endgroup$
            – Henry
            12 hours ago






          • 1




            $begingroup$
            This is an excellent hint, for students with a little knowledge of complex numbers. It also can be followed by a second hint: don’t use binomial expansion to find these!
            $endgroup$
            – Peter LeFanu Lumsdaine
            12 hours ago





















          15












          $begingroup$

          Using power series: it is well-known that $e^x=sum_{k=0}^infty frac{x^k}{k!}$ and $sin(x)=sum_{k=0}^infty (-1)^kfrac{x^{2k+1}}{(2k+1)!}$ for any real number $x$, so



          $$ e^xsin(x)=(1+x+frac{x^2}{2!}+dots+frac{x^{10}}{10!}+dots)(x-frac{x^3}{3!}+frac{x^5}{5!}-frac{x^7}{7!}+frac{x^9}{9!}+dots) $$



          By expanding, the coefficient of $x^{10}$ is $frac{1}{9!1!}-frac{1}{7!3!}+frac{1}{5!5!}-frac{1}{7!3!}+frac{1}{9!1!}$



          But this coefficient is also $frac{f^{(10)}(0)}{10!}$, so



          $$ f^{(10)}(0)=frac{10!}{9!1!}-frac{10!}{7!3!}+frac{10!}{5!5!}-frac{10!}{7!3!}+frac{10!}{9!1!} = 10 -120 + 252 - 120 +10 = 32$$






          share|cite|improve this answer









          $endgroup$









          • 2




            $begingroup$
            Take note of this solution, if the derivative at some point is needed, you don't need a symbolic expression for the $n$th derivative evaluated at some arbitrary point $x$. In some cases where a symbolic expression is not available, you can still find the $n$th derivative at some special point for arbitrary $n$. Also, there exists a general method based on Newton-Raphson division to find the $n$th derivative of an arbitrary function at some given point using some power of $log(n)$ multiplications. Some computer algebra systems use such methods to compute series expansions.
            $endgroup$
            – Count Iblis
            17 hours ago



















          7












          $begingroup$

          Use Leibniz' Rule for higher derivatives of a product:
          $$frac{d^n}{dx^n}(uv)
          =frac{d^nu}{dx^n}v+binom n1frac{d^{n-1}u}{dx^{n-1}}frac{dv}{dx}
          +binom n2frac{d^{n-2}u}{dx^{n-2}}frac{d^2v}{dx^2}+cdots+ufrac{d^nv}{dx^n} .$$

          In your case take $u=e^x$ and $v=sin x$. Since you are going to substitute $x=0$ after differentiating, all the $e^x$ terms will be $1$, all the $sin x$ terms will be $0$ and all the cos $x$ terms will be $1$ (though some of them will pick up a negative sign when you differentiate). So the answer is
          $$eqalign{0+binom{10}11&{}+binom{10}20+binom{10}3(-1)+binom{10}40+binom{10}51cr
          &qquad{}+binom{10}60+binom{10}7(-1)+binom{10}80+binom{10}91+binom{10}{10}0cr
          &=10-120+252-120+10cr
          &=32 .cr}$$






          share|cite|improve this answer









          $endgroup$





















            4












            $begingroup$

            $$(e^x(acos x+bsin x))'=e^x(acos x+bsin x)+e^x(bcos x-asin x)=e^x((a+b)cos x+(b-a)sin x).$$



            So



            $$(0,1)to(1,1)to(2,0)to(2,-2)to(0,-4)to(-4,-4)to(-8,0)to(-8,8)to(0,16)to(16,16)to(32,0).$$





            If you divide by increasing powers of $2$, in pairs, the pattern emerges, with period $8$:



            $$(0,1)to(1,1)to(1,0)to(1,-1)to(0,-1)to(-1,-1)to(-1,0)to(-1,1)to(0,1)to(1,1)to(1,0).$$






            share|cite|improve this answer











            $endgroup$





















              2












              $begingroup$

              One trick here is to use $e^{ix}=cos x+isin x$ and define $g(x)=e^xcos x$ then $f(x)$ and $g(x)$ are both real functions.



              Let $h(x)=g(x)+if(x)=e^{(1+i)x}$ then the tenth derivative of $h(x)$ is $(1+i)^{10}h(x)$ and the tenth derivative of $f(x)$ is the imaginary part of this.



              Because you only want the value at $x=0$ you can evaluate there, with $h(0)=g(0)+if(0)$






              share|cite|improve this answer









              $endgroup$





















                2












                $begingroup$

                Use the formula $(fg)^{(n)}= sumlimits_{k=0}^{n} binom {n} {k} (f)^{(k)}(g)^{(n-k)}$.






                share|cite|improve this answer









                $endgroup$





















                  1












                  $begingroup$

                  I get $f^{10}(x)=32e^xcos x$.



                  Here's what I did:
                  begin{align}f'(x)&=e^x(sin x+cos x)\
                  implies f''(x)&=2e^xcos x\
                  implies f^3(x)&=2e^x(cos x-sin x)\
                  implies f^4(x)&=2e^x(-2sin x)=-4f(x)\
                  implies f^5(x)&=-4f'(x)\
                  implies f^8(x)&=-4f^4(x)=16f(x)\
                  implies f^{10}(x)&=16f''(x)end{align}






                  share|cite|improve this answer











                  $endgroup$













                  • $begingroup$
                    Your calculation for $f^{(4)}$ is wrong. Looks like you missed a product rule.
                    $endgroup$
                    – AlexanderJ93
                    21 hours ago










                  • $begingroup$
                    Be careful: $$(e^x(g(x))'=e^xg(x)+e^xg'(x)$$ You missed the first bit in your calculation for $f^4$
                    $endgroup$
                    – Rhys Hughes
                    21 hours ago










                  • $begingroup$
                    @RhysHughes &Alexander J93 thanks
                    $endgroup$
                    – Chris Custer
                    21 hours ago



















                  0












                  $begingroup$

                  Regarding the question about looking for a pattern:



                  Repeated application of the product rule gives



                  $$ f(x) = e^x sin x$$
                  $$ f'(x) = e^x sin x + e^x cos x$$
                  $$ f''(x) = e^x sin x + e^x cos x + e^x cos x - e^x sin x = 2 e^x cos x$$
                  Is a pattern emerging?
                  $$ f^{(3)}(x) = 2 e^x cos x -2 e^x sin x$$
                  $$ f^{(4)}(x) = 2 e^x cos x -2 e^x sin x - 2 e^x sin x - 2 e^x cos x = -4 e^x sin x$$
                  Yes. We can then conclude that



                  $ f^{(6)}(x) = -8 e^x cos x$, $f^{(8)}(x) = 16 e^x sin x$, and $f^{(10)}(x) = 32 e^x cos x$



                  such that $f^{(10)}(0) = 32 $






                  share|cite|improve this answer









                  $endgroup$













                    Your Answer





                    StackExchange.ifUsing("editor", function () {
                    return StackExchange.using("mathjaxEditing", function () {
                    StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
                    StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
                    });
                    });
                    }, "mathjax-editing");

                    StackExchange.ready(function() {
                    var channelOptions = {
                    tags: "".split(" "),
                    id: "69"
                    };
                    initTagRenderer("".split(" "), "".split(" "), channelOptions);

                    StackExchange.using("externalEditor", function() {
                    // Have to fire editor after snippets, if snippets enabled
                    if (StackExchange.settings.snippets.snippetsEnabled) {
                    StackExchange.using("snippets", function() {
                    createEditor();
                    });
                    }
                    else {
                    createEditor();
                    }
                    });

                    function createEditor() {
                    StackExchange.prepareEditor({
                    heartbeatType: 'answer',
                    autoActivateHeartbeat: false,
                    convertImagesToLinks: true,
                    noModals: true,
                    showLowRepImageUploadWarning: true,
                    reputationToPostImages: 10,
                    bindNavPrevention: true,
                    postfix: "",
                    imageUploader: {
                    brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
                    contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
                    allowUrls: true
                    },
                    noCode: true, onDemand: true,
                    discardSelector: ".discard-answer"
                    ,immediatelyShowMarkdownHelp:true
                    });


                    }
                    });














                    draft saved

                    draft discarded


















                    StackExchange.ready(
                    function () {
                    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3077641%2ffinding-the-tenth-derivative%23new-answer', 'question_page');
                    }
                    );

                    Post as a guest















                    Required, but never shown

























                    9 Answers
                    9






                    active

                    oldest

                    votes








                    9 Answers
                    9






                    active

                    oldest

                    votes









                    active

                    oldest

                    votes






                    active

                    oldest

                    votes









                    26












                    $begingroup$

                    Hint:



                    $$f(x)=e^xsin x$$
                    $$f'(x)=e^x(sin x +cos x)$$
                    $$f''(x)=e^x(sin x+cos x)+e^x(cos x -sin x)=2e^x(cos x)$$
                    $$f'''(x)=e^x(2cos x)-e^x(2sin x)=2e^x(cos x-sin x)$$
                    $$f^{IV}(x)=2e^x(cos x-sin x)-2e^x(cos x+sin x)=-4e^x(sin x)=-4f(x)$$






                    share|cite|improve this answer











                    $endgroup$









                    • 10




                      $begingroup$
                      First time to see roman numerals to denote derivatives. Nice!
                      $endgroup$
                      – Taladris
                      19 hours ago






                    • 13




                      $begingroup$
                      Lower case too, awful notation if you ask me.
                      $endgroup$
                      – marshal craft
                      13 hours ago






                    • 4




                      $begingroup$
                      I have no problem with lowercase roman numerals in general, but here it looks like taking the power to the imaginary unit (times $v$)...
                      $endgroup$
                      – ilkkachu
                      9 hours ago








                    • 14




                      $begingroup$
                      There will be some confusion when you get to the tenth derivative......
                      $endgroup$
                      – Spencer
                      7 hours ago






                    • 5




                      $begingroup$
                      @Shufflepants en.wikipedia.org/wiki/Fractional_calculus
                      $endgroup$
                      – BPP
                      4 hours ago
















                    26












                    $begingroup$

                    Hint:



                    $$f(x)=e^xsin x$$
                    $$f'(x)=e^x(sin x +cos x)$$
                    $$f''(x)=e^x(sin x+cos x)+e^x(cos x -sin x)=2e^x(cos x)$$
                    $$f'''(x)=e^x(2cos x)-e^x(2sin x)=2e^x(cos x-sin x)$$
                    $$f^{IV}(x)=2e^x(cos x-sin x)-2e^x(cos x+sin x)=-4e^x(sin x)=-4f(x)$$






                    share|cite|improve this answer











                    $endgroup$









                    • 10




                      $begingroup$
                      First time to see roman numerals to denote derivatives. Nice!
                      $endgroup$
                      – Taladris
                      19 hours ago






                    • 13




                      $begingroup$
                      Lower case too, awful notation if you ask me.
                      $endgroup$
                      – marshal craft
                      13 hours ago






                    • 4




                      $begingroup$
                      I have no problem with lowercase roman numerals in general, but here it looks like taking the power to the imaginary unit (times $v$)...
                      $endgroup$
                      – ilkkachu
                      9 hours ago








                    • 14




                      $begingroup$
                      There will be some confusion when you get to the tenth derivative......
                      $endgroup$
                      – Spencer
                      7 hours ago






                    • 5




                      $begingroup$
                      @Shufflepants en.wikipedia.org/wiki/Fractional_calculus
                      $endgroup$
                      – BPP
                      4 hours ago














                    26












                    26








                    26





                    $begingroup$

                    Hint:



                    $$f(x)=e^xsin x$$
                    $$f'(x)=e^x(sin x +cos x)$$
                    $$f''(x)=e^x(sin x+cos x)+e^x(cos x -sin x)=2e^x(cos x)$$
                    $$f'''(x)=e^x(2cos x)-e^x(2sin x)=2e^x(cos x-sin x)$$
                    $$f^{IV}(x)=2e^x(cos x-sin x)-2e^x(cos x+sin x)=-4e^x(sin x)=-4f(x)$$






                    share|cite|improve this answer











                    $endgroup$



                    Hint:



                    $$f(x)=e^xsin x$$
                    $$f'(x)=e^x(sin x +cos x)$$
                    $$f''(x)=e^x(sin x+cos x)+e^x(cos x -sin x)=2e^x(cos x)$$
                    $$f'''(x)=e^x(2cos x)-e^x(2sin x)=2e^x(cos x-sin x)$$
                    $$f^{IV}(x)=2e^x(cos x-sin x)-2e^x(cos x+sin x)=-4e^x(sin x)=-4f(x)$$







                    share|cite|improve this answer














                    share|cite|improve this answer



                    share|cite|improve this answer








                    edited 5 hours ago

























                    answered 21 hours ago









                    Rhys HughesRhys Hughes

                    5,4491528




                    5,4491528








                    • 10




                      $begingroup$
                      First time to see roman numerals to denote derivatives. Nice!
                      $endgroup$
                      – Taladris
                      19 hours ago






                    • 13




                      $begingroup$
                      Lower case too, awful notation if you ask me.
                      $endgroup$
                      – marshal craft
                      13 hours ago






                    • 4




                      $begingroup$
                      I have no problem with lowercase roman numerals in general, but here it looks like taking the power to the imaginary unit (times $v$)...
                      $endgroup$
                      – ilkkachu
                      9 hours ago








                    • 14




                      $begingroup$
                      There will be some confusion when you get to the tenth derivative......
                      $endgroup$
                      – Spencer
                      7 hours ago






                    • 5




                      $begingroup$
                      @Shufflepants en.wikipedia.org/wiki/Fractional_calculus
                      $endgroup$
                      – BPP
                      4 hours ago














                    • 10




                      $begingroup$
                      First time to see roman numerals to denote derivatives. Nice!
                      $endgroup$
                      – Taladris
                      19 hours ago






                    • 13




                      $begingroup$
                      Lower case too, awful notation if you ask me.
                      $endgroup$
                      – marshal craft
                      13 hours ago






                    • 4




                      $begingroup$
                      I have no problem with lowercase roman numerals in general, but here it looks like taking the power to the imaginary unit (times $v$)...
                      $endgroup$
                      – ilkkachu
                      9 hours ago








                    • 14




                      $begingroup$
                      There will be some confusion when you get to the tenth derivative......
                      $endgroup$
                      – Spencer
                      7 hours ago






                    • 5




                      $begingroup$
                      @Shufflepants en.wikipedia.org/wiki/Fractional_calculus
                      $endgroup$
                      – BPP
                      4 hours ago








                    10




                    10




                    $begingroup$
                    First time to see roman numerals to denote derivatives. Nice!
                    $endgroup$
                    – Taladris
                    19 hours ago




                    $begingroup$
                    First time to see roman numerals to denote derivatives. Nice!
                    $endgroup$
                    – Taladris
                    19 hours ago




                    13




                    13




                    $begingroup$
                    Lower case too, awful notation if you ask me.
                    $endgroup$
                    – marshal craft
                    13 hours ago




                    $begingroup$
                    Lower case too, awful notation if you ask me.
                    $endgroup$
                    – marshal craft
                    13 hours ago




                    4




                    4




                    $begingroup$
                    I have no problem with lowercase roman numerals in general, but here it looks like taking the power to the imaginary unit (times $v$)...
                    $endgroup$
                    – ilkkachu
                    9 hours ago






                    $begingroup$
                    I have no problem with lowercase roman numerals in general, but here it looks like taking the power to the imaginary unit (times $v$)...
                    $endgroup$
                    – ilkkachu
                    9 hours ago






                    14




                    14




                    $begingroup$
                    There will be some confusion when you get to the tenth derivative......
                    $endgroup$
                    – Spencer
                    7 hours ago




                    $begingroup$
                    There will be some confusion when you get to the tenth derivative......
                    $endgroup$
                    – Spencer
                    7 hours ago




                    5




                    5




                    $begingroup$
                    @Shufflepants en.wikipedia.org/wiki/Fractional_calculus
                    $endgroup$
                    – BPP
                    4 hours ago




                    $begingroup$
                    @Shufflepants en.wikipedia.org/wiki/Fractional_calculus
                    $endgroup$
                    – BPP
                    4 hours ago











                    50












                    $begingroup$

                    Hint:



                    As $;mathrm e^xsin x=operatorname{Im}bigl(mathrm e^{(1+i)x}bigr)$, you have to find first the real and imaginary parts of $(1+i)^{10}$.






                    share|cite|improve this answer









                    $endgroup$









                    • 12




                      $begingroup$
                      This is by far the most efficient solution.
                      $endgroup$
                      – Yves Daoust
                      21 hours ago






                    • 8




                      $begingroup$
                      Knowing $(1+i)^2=2i$ helps too
                      $endgroup$
                      – Henry
                      12 hours ago






                    • 1




                      $begingroup$
                      This is an excellent hint, for students with a little knowledge of complex numbers. It also can be followed by a second hint: don’t use binomial expansion to find these!
                      $endgroup$
                      – Peter LeFanu Lumsdaine
                      12 hours ago


















                    50












                    $begingroup$

                    Hint:



                    As $;mathrm e^xsin x=operatorname{Im}bigl(mathrm e^{(1+i)x}bigr)$, you have to find first the real and imaginary parts of $(1+i)^{10}$.






                    share|cite|improve this answer









                    $endgroup$









                    • 12




                      $begingroup$
                      This is by far the most efficient solution.
                      $endgroup$
                      – Yves Daoust
                      21 hours ago






                    • 8




                      $begingroup$
                      Knowing $(1+i)^2=2i$ helps too
                      $endgroup$
                      – Henry
                      12 hours ago






                    • 1




                      $begingroup$
                      This is an excellent hint, for students with a little knowledge of complex numbers. It also can be followed by a second hint: don’t use binomial expansion to find these!
                      $endgroup$
                      – Peter LeFanu Lumsdaine
                      12 hours ago
















                    50












                    50








                    50





                    $begingroup$

                    Hint:



                    As $;mathrm e^xsin x=operatorname{Im}bigl(mathrm e^{(1+i)x}bigr)$, you have to find first the real and imaginary parts of $(1+i)^{10}$.






                    share|cite|improve this answer









                    $endgroup$



                    Hint:



                    As $;mathrm e^xsin x=operatorname{Im}bigl(mathrm e^{(1+i)x}bigr)$, you have to find first the real and imaginary parts of $(1+i)^{10}$.







                    share|cite|improve this answer












                    share|cite|improve this answer



                    share|cite|improve this answer










                    answered 21 hours ago









                    BernardBernard

                    119k740113




                    119k740113








                    • 12




                      $begingroup$
                      This is by far the most efficient solution.
                      $endgroup$
                      – Yves Daoust
                      21 hours ago






                    • 8




                      $begingroup$
                      Knowing $(1+i)^2=2i$ helps too
                      $endgroup$
                      – Henry
                      12 hours ago






                    • 1




                      $begingroup$
                      This is an excellent hint, for students with a little knowledge of complex numbers. It also can be followed by a second hint: don’t use binomial expansion to find these!
                      $endgroup$
                      – Peter LeFanu Lumsdaine
                      12 hours ago
















                    • 12




                      $begingroup$
                      This is by far the most efficient solution.
                      $endgroup$
                      – Yves Daoust
                      21 hours ago






                    • 8




                      $begingroup$
                      Knowing $(1+i)^2=2i$ helps too
                      $endgroup$
                      – Henry
                      12 hours ago






                    • 1




                      $begingroup$
                      This is an excellent hint, for students with a little knowledge of complex numbers. It also can be followed by a second hint: don’t use binomial expansion to find these!
                      $endgroup$
                      – Peter LeFanu Lumsdaine
                      12 hours ago










                    12




                    12




                    $begingroup$
                    This is by far the most efficient solution.
                    $endgroup$
                    – Yves Daoust
                    21 hours ago




                    $begingroup$
                    This is by far the most efficient solution.
                    $endgroup$
                    – Yves Daoust
                    21 hours ago




                    8




                    8




                    $begingroup$
                    Knowing $(1+i)^2=2i$ helps too
                    $endgroup$
                    – Henry
                    12 hours ago




                    $begingroup$
                    Knowing $(1+i)^2=2i$ helps too
                    $endgroup$
                    – Henry
                    12 hours ago




                    1




                    1




                    $begingroup$
                    This is an excellent hint, for students with a little knowledge of complex numbers. It also can be followed by a second hint: don’t use binomial expansion to find these!
                    $endgroup$
                    – Peter LeFanu Lumsdaine
                    12 hours ago






                    $begingroup$
                    This is an excellent hint, for students with a little knowledge of complex numbers. It also can be followed by a second hint: don’t use binomial expansion to find these!
                    $endgroup$
                    – Peter LeFanu Lumsdaine
                    12 hours ago













                    15












                    $begingroup$

                    Using power series: it is well-known that $e^x=sum_{k=0}^infty frac{x^k}{k!}$ and $sin(x)=sum_{k=0}^infty (-1)^kfrac{x^{2k+1}}{(2k+1)!}$ for any real number $x$, so



                    $$ e^xsin(x)=(1+x+frac{x^2}{2!}+dots+frac{x^{10}}{10!}+dots)(x-frac{x^3}{3!}+frac{x^5}{5!}-frac{x^7}{7!}+frac{x^9}{9!}+dots) $$



                    By expanding, the coefficient of $x^{10}$ is $frac{1}{9!1!}-frac{1}{7!3!}+frac{1}{5!5!}-frac{1}{7!3!}+frac{1}{9!1!}$



                    But this coefficient is also $frac{f^{(10)}(0)}{10!}$, so



                    $$ f^{(10)}(0)=frac{10!}{9!1!}-frac{10!}{7!3!}+frac{10!}{5!5!}-frac{10!}{7!3!}+frac{10!}{9!1!} = 10 -120 + 252 - 120 +10 = 32$$






                    share|cite|improve this answer









                    $endgroup$









                    • 2




                      $begingroup$
                      Take note of this solution, if the derivative at some point is needed, you don't need a symbolic expression for the $n$th derivative evaluated at some arbitrary point $x$. In some cases where a symbolic expression is not available, you can still find the $n$th derivative at some special point for arbitrary $n$. Also, there exists a general method based on Newton-Raphson division to find the $n$th derivative of an arbitrary function at some given point using some power of $log(n)$ multiplications. Some computer algebra systems use such methods to compute series expansions.
                      $endgroup$
                      – Count Iblis
                      17 hours ago
















                    15












                    $begingroup$

                    Using power series: it is well-known that $e^x=sum_{k=0}^infty frac{x^k}{k!}$ and $sin(x)=sum_{k=0}^infty (-1)^kfrac{x^{2k+1}}{(2k+1)!}$ for any real number $x$, so



                    $$ e^xsin(x)=(1+x+frac{x^2}{2!}+dots+frac{x^{10}}{10!}+dots)(x-frac{x^3}{3!}+frac{x^5}{5!}-frac{x^7}{7!}+frac{x^9}{9!}+dots) $$



                    By expanding, the coefficient of $x^{10}$ is $frac{1}{9!1!}-frac{1}{7!3!}+frac{1}{5!5!}-frac{1}{7!3!}+frac{1}{9!1!}$



                    But this coefficient is also $frac{f^{(10)}(0)}{10!}$, so



                    $$ f^{(10)}(0)=frac{10!}{9!1!}-frac{10!}{7!3!}+frac{10!}{5!5!}-frac{10!}{7!3!}+frac{10!}{9!1!} = 10 -120 + 252 - 120 +10 = 32$$






                    share|cite|improve this answer









                    $endgroup$









                    • 2




                      $begingroup$
                      Take note of this solution, if the derivative at some point is needed, you don't need a symbolic expression for the $n$th derivative evaluated at some arbitrary point $x$. In some cases where a symbolic expression is not available, you can still find the $n$th derivative at some special point for arbitrary $n$. Also, there exists a general method based on Newton-Raphson division to find the $n$th derivative of an arbitrary function at some given point using some power of $log(n)$ multiplications. Some computer algebra systems use such methods to compute series expansions.
                      $endgroup$
                      – Count Iblis
                      17 hours ago














                    15












                    15








                    15





                    $begingroup$

                    Using power series: it is well-known that $e^x=sum_{k=0}^infty frac{x^k}{k!}$ and $sin(x)=sum_{k=0}^infty (-1)^kfrac{x^{2k+1}}{(2k+1)!}$ for any real number $x$, so



                    $$ e^xsin(x)=(1+x+frac{x^2}{2!}+dots+frac{x^{10}}{10!}+dots)(x-frac{x^3}{3!}+frac{x^5}{5!}-frac{x^7}{7!}+frac{x^9}{9!}+dots) $$



                    By expanding, the coefficient of $x^{10}$ is $frac{1}{9!1!}-frac{1}{7!3!}+frac{1}{5!5!}-frac{1}{7!3!}+frac{1}{9!1!}$



                    But this coefficient is also $frac{f^{(10)}(0)}{10!}$, so



                    $$ f^{(10)}(0)=frac{10!}{9!1!}-frac{10!}{7!3!}+frac{10!}{5!5!}-frac{10!}{7!3!}+frac{10!}{9!1!} = 10 -120 + 252 - 120 +10 = 32$$






                    share|cite|improve this answer









                    $endgroup$



                    Using power series: it is well-known that $e^x=sum_{k=0}^infty frac{x^k}{k!}$ and $sin(x)=sum_{k=0}^infty (-1)^kfrac{x^{2k+1}}{(2k+1)!}$ for any real number $x$, so



                    $$ e^xsin(x)=(1+x+frac{x^2}{2!}+dots+frac{x^{10}}{10!}+dots)(x-frac{x^3}{3!}+frac{x^5}{5!}-frac{x^7}{7!}+frac{x^9}{9!}+dots) $$



                    By expanding, the coefficient of $x^{10}$ is $frac{1}{9!1!}-frac{1}{7!3!}+frac{1}{5!5!}-frac{1}{7!3!}+frac{1}{9!1!}$



                    But this coefficient is also $frac{f^{(10)}(0)}{10!}$, so



                    $$ f^{(10)}(0)=frac{10!}{9!1!}-frac{10!}{7!3!}+frac{10!}{5!5!}-frac{10!}{7!3!}+frac{10!}{9!1!} = 10 -120 + 252 - 120 +10 = 32$$







                    share|cite|improve this answer












                    share|cite|improve this answer



                    share|cite|improve this answer










                    answered 18 hours ago









                    TaladrisTaladris

                    4,84231933




                    4,84231933








                    • 2




                      $begingroup$
                      Take note of this solution, if the derivative at some point is needed, you don't need a symbolic expression for the $n$th derivative evaluated at some arbitrary point $x$. In some cases where a symbolic expression is not available, you can still find the $n$th derivative at some special point for arbitrary $n$. Also, there exists a general method based on Newton-Raphson division to find the $n$th derivative of an arbitrary function at some given point using some power of $log(n)$ multiplications. Some computer algebra systems use such methods to compute series expansions.
                      $endgroup$
                      – Count Iblis
                      17 hours ago














                    • 2




                      $begingroup$
                      Take note of this solution, if the derivative at some point is needed, you don't need a symbolic expression for the $n$th derivative evaluated at some arbitrary point $x$. In some cases where a symbolic expression is not available, you can still find the $n$th derivative at some special point for arbitrary $n$. Also, there exists a general method based on Newton-Raphson division to find the $n$th derivative of an arbitrary function at some given point using some power of $log(n)$ multiplications. Some computer algebra systems use such methods to compute series expansions.
                      $endgroup$
                      – Count Iblis
                      17 hours ago








                    2




                    2




                    $begingroup$
                    Take note of this solution, if the derivative at some point is needed, you don't need a symbolic expression for the $n$th derivative evaluated at some arbitrary point $x$. In some cases where a symbolic expression is not available, you can still find the $n$th derivative at some special point for arbitrary $n$. Also, there exists a general method based on Newton-Raphson division to find the $n$th derivative of an arbitrary function at some given point using some power of $log(n)$ multiplications. Some computer algebra systems use such methods to compute series expansions.
                    $endgroup$
                    – Count Iblis
                    17 hours ago




                    $begingroup$
                    Take note of this solution, if the derivative at some point is needed, you don't need a symbolic expression for the $n$th derivative evaluated at some arbitrary point $x$. In some cases where a symbolic expression is not available, you can still find the $n$th derivative at some special point for arbitrary $n$. Also, there exists a general method based on Newton-Raphson division to find the $n$th derivative of an arbitrary function at some given point using some power of $log(n)$ multiplications. Some computer algebra systems use such methods to compute series expansions.
                    $endgroup$
                    – Count Iblis
                    17 hours ago











                    7












                    $begingroup$

                    Use Leibniz' Rule for higher derivatives of a product:
                    $$frac{d^n}{dx^n}(uv)
                    =frac{d^nu}{dx^n}v+binom n1frac{d^{n-1}u}{dx^{n-1}}frac{dv}{dx}
                    +binom n2frac{d^{n-2}u}{dx^{n-2}}frac{d^2v}{dx^2}+cdots+ufrac{d^nv}{dx^n} .$$

                    In your case take $u=e^x$ and $v=sin x$. Since you are going to substitute $x=0$ after differentiating, all the $e^x$ terms will be $1$, all the $sin x$ terms will be $0$ and all the cos $x$ terms will be $1$ (though some of them will pick up a negative sign when you differentiate). So the answer is
                    $$eqalign{0+binom{10}11&{}+binom{10}20+binom{10}3(-1)+binom{10}40+binom{10}51cr
                    &qquad{}+binom{10}60+binom{10}7(-1)+binom{10}80+binom{10}91+binom{10}{10}0cr
                    &=10-120+252-120+10cr
                    &=32 .cr}$$






                    share|cite|improve this answer









                    $endgroup$


















                      7












                      $begingroup$

                      Use Leibniz' Rule for higher derivatives of a product:
                      $$frac{d^n}{dx^n}(uv)
                      =frac{d^nu}{dx^n}v+binom n1frac{d^{n-1}u}{dx^{n-1}}frac{dv}{dx}
                      +binom n2frac{d^{n-2}u}{dx^{n-2}}frac{d^2v}{dx^2}+cdots+ufrac{d^nv}{dx^n} .$$

                      In your case take $u=e^x$ and $v=sin x$. Since you are going to substitute $x=0$ after differentiating, all the $e^x$ terms will be $1$, all the $sin x$ terms will be $0$ and all the cos $x$ terms will be $1$ (though some of them will pick up a negative sign when you differentiate). So the answer is
                      $$eqalign{0+binom{10}11&{}+binom{10}20+binom{10}3(-1)+binom{10}40+binom{10}51cr
                      &qquad{}+binom{10}60+binom{10}7(-1)+binom{10}80+binom{10}91+binom{10}{10}0cr
                      &=10-120+252-120+10cr
                      &=32 .cr}$$






                      share|cite|improve this answer









                      $endgroup$
















                        7












                        7








                        7





                        $begingroup$

                        Use Leibniz' Rule for higher derivatives of a product:
                        $$frac{d^n}{dx^n}(uv)
                        =frac{d^nu}{dx^n}v+binom n1frac{d^{n-1}u}{dx^{n-1}}frac{dv}{dx}
                        +binom n2frac{d^{n-2}u}{dx^{n-2}}frac{d^2v}{dx^2}+cdots+ufrac{d^nv}{dx^n} .$$

                        In your case take $u=e^x$ and $v=sin x$. Since you are going to substitute $x=0$ after differentiating, all the $e^x$ terms will be $1$, all the $sin x$ terms will be $0$ and all the cos $x$ terms will be $1$ (though some of them will pick up a negative sign when you differentiate). So the answer is
                        $$eqalign{0+binom{10}11&{}+binom{10}20+binom{10}3(-1)+binom{10}40+binom{10}51cr
                        &qquad{}+binom{10}60+binom{10}7(-1)+binom{10}80+binom{10}91+binom{10}{10}0cr
                        &=10-120+252-120+10cr
                        &=32 .cr}$$






                        share|cite|improve this answer









                        $endgroup$



                        Use Leibniz' Rule for higher derivatives of a product:
                        $$frac{d^n}{dx^n}(uv)
                        =frac{d^nu}{dx^n}v+binom n1frac{d^{n-1}u}{dx^{n-1}}frac{dv}{dx}
                        +binom n2frac{d^{n-2}u}{dx^{n-2}}frac{d^2v}{dx^2}+cdots+ufrac{d^nv}{dx^n} .$$

                        In your case take $u=e^x$ and $v=sin x$. Since you are going to substitute $x=0$ after differentiating, all the $e^x$ terms will be $1$, all the $sin x$ terms will be $0$ and all the cos $x$ terms will be $1$ (though some of them will pick up a negative sign when you differentiate). So the answer is
                        $$eqalign{0+binom{10}11&{}+binom{10}20+binom{10}3(-1)+binom{10}40+binom{10}51cr
                        &qquad{}+binom{10}60+binom{10}7(-1)+binom{10}80+binom{10}91+binom{10}{10}0cr
                        &=10-120+252-120+10cr
                        &=32 .cr}$$







                        share|cite|improve this answer












                        share|cite|improve this answer



                        share|cite|improve this answer










                        answered 21 hours ago









                        DavidDavid

                        68.1k664126




                        68.1k664126























                            4












                            $begingroup$

                            $$(e^x(acos x+bsin x))'=e^x(acos x+bsin x)+e^x(bcos x-asin x)=e^x((a+b)cos x+(b-a)sin x).$$



                            So



                            $$(0,1)to(1,1)to(2,0)to(2,-2)to(0,-4)to(-4,-4)to(-8,0)to(-8,8)to(0,16)to(16,16)to(32,0).$$





                            If you divide by increasing powers of $2$, in pairs, the pattern emerges, with period $8$:



                            $$(0,1)to(1,1)to(1,0)to(1,-1)to(0,-1)to(-1,-1)to(-1,0)to(-1,1)to(0,1)to(1,1)to(1,0).$$






                            share|cite|improve this answer











                            $endgroup$


















                              4












                              $begingroup$

                              $$(e^x(acos x+bsin x))'=e^x(acos x+bsin x)+e^x(bcos x-asin x)=e^x((a+b)cos x+(b-a)sin x).$$



                              So



                              $$(0,1)to(1,1)to(2,0)to(2,-2)to(0,-4)to(-4,-4)to(-8,0)to(-8,8)to(0,16)to(16,16)to(32,0).$$





                              If you divide by increasing powers of $2$, in pairs, the pattern emerges, with period $8$:



                              $$(0,1)to(1,1)to(1,0)to(1,-1)to(0,-1)to(-1,-1)to(-1,0)to(-1,1)to(0,1)to(1,1)to(1,0).$$






                              share|cite|improve this answer











                              $endgroup$
















                                4












                                4








                                4





                                $begingroup$

                                $$(e^x(acos x+bsin x))'=e^x(acos x+bsin x)+e^x(bcos x-asin x)=e^x((a+b)cos x+(b-a)sin x).$$



                                So



                                $$(0,1)to(1,1)to(2,0)to(2,-2)to(0,-4)to(-4,-4)to(-8,0)to(-8,8)to(0,16)to(16,16)to(32,0).$$





                                If you divide by increasing powers of $2$, in pairs, the pattern emerges, with period $8$:



                                $$(0,1)to(1,1)to(1,0)to(1,-1)to(0,-1)to(-1,-1)to(-1,0)to(-1,1)to(0,1)to(1,1)to(1,0).$$






                                share|cite|improve this answer











                                $endgroup$



                                $$(e^x(acos x+bsin x))'=e^x(acos x+bsin x)+e^x(bcos x-asin x)=e^x((a+b)cos x+(b-a)sin x).$$



                                So



                                $$(0,1)to(1,1)to(2,0)to(2,-2)to(0,-4)to(-4,-4)to(-8,0)to(-8,8)to(0,16)to(16,16)to(32,0).$$





                                If you divide by increasing powers of $2$, in pairs, the pattern emerges, with period $8$:



                                $$(0,1)to(1,1)to(1,0)to(1,-1)to(0,-1)to(-1,-1)to(-1,0)to(-1,1)to(0,1)to(1,1)to(1,0).$$







                                share|cite|improve this answer














                                share|cite|improve this answer



                                share|cite|improve this answer








                                edited 21 hours ago

























                                answered 21 hours ago









                                Yves DaoustYves Daoust

                                125k671222




                                125k671222























                                    2












                                    $begingroup$

                                    One trick here is to use $e^{ix}=cos x+isin x$ and define $g(x)=e^xcos x$ then $f(x)$ and $g(x)$ are both real functions.



                                    Let $h(x)=g(x)+if(x)=e^{(1+i)x}$ then the tenth derivative of $h(x)$ is $(1+i)^{10}h(x)$ and the tenth derivative of $f(x)$ is the imaginary part of this.



                                    Because you only want the value at $x=0$ you can evaluate there, with $h(0)=g(0)+if(0)$






                                    share|cite|improve this answer









                                    $endgroup$


















                                      2












                                      $begingroup$

                                      One trick here is to use $e^{ix}=cos x+isin x$ and define $g(x)=e^xcos x$ then $f(x)$ and $g(x)$ are both real functions.



                                      Let $h(x)=g(x)+if(x)=e^{(1+i)x}$ then the tenth derivative of $h(x)$ is $(1+i)^{10}h(x)$ and the tenth derivative of $f(x)$ is the imaginary part of this.



                                      Because you only want the value at $x=0$ you can evaluate there, with $h(0)=g(0)+if(0)$






                                      share|cite|improve this answer









                                      $endgroup$
















                                        2












                                        2








                                        2





                                        $begingroup$

                                        One trick here is to use $e^{ix}=cos x+isin x$ and define $g(x)=e^xcos x$ then $f(x)$ and $g(x)$ are both real functions.



                                        Let $h(x)=g(x)+if(x)=e^{(1+i)x}$ then the tenth derivative of $h(x)$ is $(1+i)^{10}h(x)$ and the tenth derivative of $f(x)$ is the imaginary part of this.



                                        Because you only want the value at $x=0$ you can evaluate there, with $h(0)=g(0)+if(0)$






                                        share|cite|improve this answer









                                        $endgroup$



                                        One trick here is to use $e^{ix}=cos x+isin x$ and define $g(x)=e^xcos x$ then $f(x)$ and $g(x)$ are both real functions.



                                        Let $h(x)=g(x)+if(x)=e^{(1+i)x}$ then the tenth derivative of $h(x)$ is $(1+i)^{10}h(x)$ and the tenth derivative of $f(x)$ is the imaginary part of this.



                                        Because you only want the value at $x=0$ you can evaluate there, with $h(0)=g(0)+if(0)$







                                        share|cite|improve this answer












                                        share|cite|improve this answer



                                        share|cite|improve this answer










                                        answered 21 hours ago









                                        Mark BennetMark Bennet

                                        80.8k981179




                                        80.8k981179























                                            2












                                            $begingroup$

                                            Use the formula $(fg)^{(n)}= sumlimits_{k=0}^{n} binom {n} {k} (f)^{(k)}(g)^{(n-k)}$.






                                            share|cite|improve this answer









                                            $endgroup$


















                                              2












                                              $begingroup$

                                              Use the formula $(fg)^{(n)}= sumlimits_{k=0}^{n} binom {n} {k} (f)^{(k)}(g)^{(n-k)}$.






                                              share|cite|improve this answer









                                              $endgroup$
















                                                2












                                                2








                                                2





                                                $begingroup$

                                                Use the formula $(fg)^{(n)}= sumlimits_{k=0}^{n} binom {n} {k} (f)^{(k)}(g)^{(n-k)}$.






                                                share|cite|improve this answer









                                                $endgroup$



                                                Use the formula $(fg)^{(n)}= sumlimits_{k=0}^{n} binom {n} {k} (f)^{(k)}(g)^{(n-k)}$.







                                                share|cite|improve this answer












                                                share|cite|improve this answer



                                                share|cite|improve this answer










                                                answered 21 hours ago









                                                Kavi Rama MurthyKavi Rama Murthy

                                                54.1k32055




                                                54.1k32055























                                                    1












                                                    $begingroup$

                                                    I get $f^{10}(x)=32e^xcos x$.



                                                    Here's what I did:
                                                    begin{align}f'(x)&=e^x(sin x+cos x)\
                                                    implies f''(x)&=2e^xcos x\
                                                    implies f^3(x)&=2e^x(cos x-sin x)\
                                                    implies f^4(x)&=2e^x(-2sin x)=-4f(x)\
                                                    implies f^5(x)&=-4f'(x)\
                                                    implies f^8(x)&=-4f^4(x)=16f(x)\
                                                    implies f^{10}(x)&=16f''(x)end{align}






                                                    share|cite|improve this answer











                                                    $endgroup$













                                                    • $begingroup$
                                                      Your calculation for $f^{(4)}$ is wrong. Looks like you missed a product rule.
                                                      $endgroup$
                                                      – AlexanderJ93
                                                      21 hours ago










                                                    • $begingroup$
                                                      Be careful: $$(e^x(g(x))'=e^xg(x)+e^xg'(x)$$ You missed the first bit in your calculation for $f^4$
                                                      $endgroup$
                                                      – Rhys Hughes
                                                      21 hours ago










                                                    • $begingroup$
                                                      @RhysHughes &Alexander J93 thanks
                                                      $endgroup$
                                                      – Chris Custer
                                                      21 hours ago
















                                                    1












                                                    $begingroup$

                                                    I get $f^{10}(x)=32e^xcos x$.



                                                    Here's what I did:
                                                    begin{align}f'(x)&=e^x(sin x+cos x)\
                                                    implies f''(x)&=2e^xcos x\
                                                    implies f^3(x)&=2e^x(cos x-sin x)\
                                                    implies f^4(x)&=2e^x(-2sin x)=-4f(x)\
                                                    implies f^5(x)&=-4f'(x)\
                                                    implies f^8(x)&=-4f^4(x)=16f(x)\
                                                    implies f^{10}(x)&=16f''(x)end{align}






                                                    share|cite|improve this answer











                                                    $endgroup$













                                                    • $begingroup$
                                                      Your calculation for $f^{(4)}$ is wrong. Looks like you missed a product rule.
                                                      $endgroup$
                                                      – AlexanderJ93
                                                      21 hours ago










                                                    • $begingroup$
                                                      Be careful: $$(e^x(g(x))'=e^xg(x)+e^xg'(x)$$ You missed the first bit in your calculation for $f^4$
                                                      $endgroup$
                                                      – Rhys Hughes
                                                      21 hours ago










                                                    • $begingroup$
                                                      @RhysHughes &Alexander J93 thanks
                                                      $endgroup$
                                                      – Chris Custer
                                                      21 hours ago














                                                    1












                                                    1








                                                    1





                                                    $begingroup$

                                                    I get $f^{10}(x)=32e^xcos x$.



                                                    Here's what I did:
                                                    begin{align}f'(x)&=e^x(sin x+cos x)\
                                                    implies f''(x)&=2e^xcos x\
                                                    implies f^3(x)&=2e^x(cos x-sin x)\
                                                    implies f^4(x)&=2e^x(-2sin x)=-4f(x)\
                                                    implies f^5(x)&=-4f'(x)\
                                                    implies f^8(x)&=-4f^4(x)=16f(x)\
                                                    implies f^{10}(x)&=16f''(x)end{align}






                                                    share|cite|improve this answer











                                                    $endgroup$



                                                    I get $f^{10}(x)=32e^xcos x$.



                                                    Here's what I did:
                                                    begin{align}f'(x)&=e^x(sin x+cos x)\
                                                    implies f''(x)&=2e^xcos x\
                                                    implies f^3(x)&=2e^x(cos x-sin x)\
                                                    implies f^4(x)&=2e^x(-2sin x)=-4f(x)\
                                                    implies f^5(x)&=-4f'(x)\
                                                    implies f^8(x)&=-4f^4(x)=16f(x)\
                                                    implies f^{10}(x)&=16f''(x)end{align}







                                                    share|cite|improve this answer














                                                    share|cite|improve this answer



                                                    share|cite|improve this answer








                                                    edited 11 hours ago









                                                    lioness99a

                                                    3,6662727




                                                    3,6662727










                                                    answered 21 hours ago









                                                    Chris CusterChris Custer

                                                    11.3k3824




                                                    11.3k3824












                                                    • $begingroup$
                                                      Your calculation for $f^{(4)}$ is wrong. Looks like you missed a product rule.
                                                      $endgroup$
                                                      – AlexanderJ93
                                                      21 hours ago










                                                    • $begingroup$
                                                      Be careful: $$(e^x(g(x))'=e^xg(x)+e^xg'(x)$$ You missed the first bit in your calculation for $f^4$
                                                      $endgroup$
                                                      – Rhys Hughes
                                                      21 hours ago










                                                    • $begingroup$
                                                      @RhysHughes &Alexander J93 thanks
                                                      $endgroup$
                                                      – Chris Custer
                                                      21 hours ago


















                                                    • $begingroup$
                                                      Your calculation for $f^{(4)}$ is wrong. Looks like you missed a product rule.
                                                      $endgroup$
                                                      – AlexanderJ93
                                                      21 hours ago










                                                    • $begingroup$
                                                      Be careful: $$(e^x(g(x))'=e^xg(x)+e^xg'(x)$$ You missed the first bit in your calculation for $f^4$
                                                      $endgroup$
                                                      – Rhys Hughes
                                                      21 hours ago










                                                    • $begingroup$
                                                      @RhysHughes &Alexander J93 thanks
                                                      $endgroup$
                                                      – Chris Custer
                                                      21 hours ago
















                                                    $begingroup$
                                                    Your calculation for $f^{(4)}$ is wrong. Looks like you missed a product rule.
                                                    $endgroup$
                                                    – AlexanderJ93
                                                    21 hours ago




                                                    $begingroup$
                                                    Your calculation for $f^{(4)}$ is wrong. Looks like you missed a product rule.
                                                    $endgroup$
                                                    – AlexanderJ93
                                                    21 hours ago












                                                    $begingroup$
                                                    Be careful: $$(e^x(g(x))'=e^xg(x)+e^xg'(x)$$ You missed the first bit in your calculation for $f^4$
                                                    $endgroup$
                                                    – Rhys Hughes
                                                    21 hours ago




                                                    $begingroup$
                                                    Be careful: $$(e^x(g(x))'=e^xg(x)+e^xg'(x)$$ You missed the first bit in your calculation for $f^4$
                                                    $endgroup$
                                                    – Rhys Hughes
                                                    21 hours ago












                                                    $begingroup$
                                                    @RhysHughes &Alexander J93 thanks
                                                    $endgroup$
                                                    – Chris Custer
                                                    21 hours ago




                                                    $begingroup$
                                                    @RhysHughes &Alexander J93 thanks
                                                    $endgroup$
                                                    – Chris Custer
                                                    21 hours ago











                                                    0












                                                    $begingroup$

                                                    Regarding the question about looking for a pattern:



                                                    Repeated application of the product rule gives



                                                    $$ f(x) = e^x sin x$$
                                                    $$ f'(x) = e^x sin x + e^x cos x$$
                                                    $$ f''(x) = e^x sin x + e^x cos x + e^x cos x - e^x sin x = 2 e^x cos x$$
                                                    Is a pattern emerging?
                                                    $$ f^{(3)}(x) = 2 e^x cos x -2 e^x sin x$$
                                                    $$ f^{(4)}(x) = 2 e^x cos x -2 e^x sin x - 2 e^x sin x - 2 e^x cos x = -4 e^x sin x$$
                                                    Yes. We can then conclude that



                                                    $ f^{(6)}(x) = -8 e^x cos x$, $f^{(8)}(x) = 16 e^x sin x$, and $f^{(10)}(x) = 32 e^x cos x$



                                                    such that $f^{(10)}(0) = 32 $






                                                    share|cite|improve this answer









                                                    $endgroup$


















                                                      0












                                                      $begingroup$

                                                      Regarding the question about looking for a pattern:



                                                      Repeated application of the product rule gives



                                                      $$ f(x) = e^x sin x$$
                                                      $$ f'(x) = e^x sin x + e^x cos x$$
                                                      $$ f''(x) = e^x sin x + e^x cos x + e^x cos x - e^x sin x = 2 e^x cos x$$
                                                      Is a pattern emerging?
                                                      $$ f^{(3)}(x) = 2 e^x cos x -2 e^x sin x$$
                                                      $$ f^{(4)}(x) = 2 e^x cos x -2 e^x sin x - 2 e^x sin x - 2 e^x cos x = -4 e^x sin x$$
                                                      Yes. We can then conclude that



                                                      $ f^{(6)}(x) = -8 e^x cos x$, $f^{(8)}(x) = 16 e^x sin x$, and $f^{(10)}(x) = 32 e^x cos x$



                                                      such that $f^{(10)}(0) = 32 $






                                                      share|cite|improve this answer









                                                      $endgroup$
















                                                        0












                                                        0








                                                        0





                                                        $begingroup$

                                                        Regarding the question about looking for a pattern:



                                                        Repeated application of the product rule gives



                                                        $$ f(x) = e^x sin x$$
                                                        $$ f'(x) = e^x sin x + e^x cos x$$
                                                        $$ f''(x) = e^x sin x + e^x cos x + e^x cos x - e^x sin x = 2 e^x cos x$$
                                                        Is a pattern emerging?
                                                        $$ f^{(3)}(x) = 2 e^x cos x -2 e^x sin x$$
                                                        $$ f^{(4)}(x) = 2 e^x cos x -2 e^x sin x - 2 e^x sin x - 2 e^x cos x = -4 e^x sin x$$
                                                        Yes. We can then conclude that



                                                        $ f^{(6)}(x) = -8 e^x cos x$, $f^{(8)}(x) = 16 e^x sin x$, and $f^{(10)}(x) = 32 e^x cos x$



                                                        such that $f^{(10)}(0) = 32 $






                                                        share|cite|improve this answer









                                                        $endgroup$



                                                        Regarding the question about looking for a pattern:



                                                        Repeated application of the product rule gives



                                                        $$ f(x) = e^x sin x$$
                                                        $$ f'(x) = e^x sin x + e^x cos x$$
                                                        $$ f''(x) = e^x sin x + e^x cos x + e^x cos x - e^x sin x = 2 e^x cos x$$
                                                        Is a pattern emerging?
                                                        $$ f^{(3)}(x) = 2 e^x cos x -2 e^x sin x$$
                                                        $$ f^{(4)}(x) = 2 e^x cos x -2 e^x sin x - 2 e^x sin x - 2 e^x cos x = -4 e^x sin x$$
                                                        Yes. We can then conclude that



                                                        $ f^{(6)}(x) = -8 e^x cos x$, $f^{(8)}(x) = 16 e^x sin x$, and $f^{(10)}(x) = 32 e^x cos x$



                                                        such that $f^{(10)}(0) = 32 $







                                                        share|cite|improve this answer












                                                        share|cite|improve this answer



                                                        share|cite|improve this answer










                                                        answered 1 hour ago









                                                        Terje D.Terje D.

                                                        1213




                                                        1213






























                                                            draft saved

                                                            draft discarded




















































                                                            Thanks for contributing an answer to Mathematics Stack Exchange!


                                                            • Please be sure to answer the question. Provide details and share your research!

                                                            But avoid



                                                            • Asking for help, clarification, or responding to other answers.

                                                            • Making statements based on opinion; back them up with references or personal experience.


                                                            Use MathJax to format equations. MathJax reference.


                                                            To learn more, see our tips on writing great answers.




                                                            draft saved


                                                            draft discarded














                                                            StackExchange.ready(
                                                            function () {
                                                            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3077641%2ffinding-the-tenth-derivative%23new-answer', 'question_page');
                                                            }
                                                            );

                                                            Post as a guest















                                                            Required, but never shown





















































                                                            Required, but never shown














                                                            Required, but never shown












                                                            Required, but never shown







                                                            Required, but never shown

































                                                            Required, but never shown














                                                            Required, but never shown












                                                            Required, but never shown







                                                            Required, but never shown







                                                            Popular posts from this blog

                                                            Ponta tanko

                                                            Tantalo (mitologio)

                                                            Erzsébet Schaár