How to solve $int sin^3(x) cos^2(x) dx$ with integration by parts?












0












$begingroup$


Surely it's easier to use substitution and trig identities, but I wonder if it's possible to use integration by parts. Here's what I tried



$$int sin^3(x) cos^2(x)dx$$



Let: $u'=cos (x), u = sin (x), v = sin (x) , v'=cos (x)$



$$int v^3 u'^2$$



And here's where I'm stuck, how do I go about this? I'm not sure how to do integration by parts with such exponents










share|cite|improve this question











$endgroup$








  • 2




    $begingroup$
    dont forget the integration symbol dx, you must replace it with some d(new variable) for the integral to make any sense
    $endgroup$
    – mathreadler
    Jan 31 '18 at 20:16


















0












$begingroup$


Surely it's easier to use substitution and trig identities, but I wonder if it's possible to use integration by parts. Here's what I tried



$$int sin^3(x) cos^2(x)dx$$



Let: $u'=cos (x), u = sin (x), v = sin (x) , v'=cos (x)$



$$int v^3 u'^2$$



And here's where I'm stuck, how do I go about this? I'm not sure how to do integration by parts with such exponents










share|cite|improve this question











$endgroup$








  • 2




    $begingroup$
    dont forget the integration symbol dx, you must replace it with some d(new variable) for the integral to make any sense
    $endgroup$
    – mathreadler
    Jan 31 '18 at 20:16
















0












0








0





$begingroup$


Surely it's easier to use substitution and trig identities, but I wonder if it's possible to use integration by parts. Here's what I tried



$$int sin^3(x) cos^2(x)dx$$



Let: $u'=cos (x), u = sin (x), v = sin (x) , v'=cos (x)$



$$int v^3 u'^2$$



And here's where I'm stuck, how do I go about this? I'm not sure how to do integration by parts with such exponents










share|cite|improve this question











$endgroup$




Surely it's easier to use substitution and trig identities, but I wonder if it's possible to use integration by parts. Here's what I tried



$$int sin^3(x) cos^2(x)dx$$



Let: $u'=cos (x), u = sin (x), v = sin (x) , v'=cos (x)$



$$int v^3 u'^2$$



And here's where I'm stuck, how do I go about this? I'm not sure how to do integration by parts with such exponents







calculus real-analysis integration trigonometry






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 31 '18 at 20:25









Michael Rozenberg

102k1791195




102k1791195










asked Jan 31 '18 at 20:11









TreyTrey

309113




309113








  • 2




    $begingroup$
    dont forget the integration symbol dx, you must replace it with some d(new variable) for the integral to make any sense
    $endgroup$
    – mathreadler
    Jan 31 '18 at 20:16
















  • 2




    $begingroup$
    dont forget the integration symbol dx, you must replace it with some d(new variable) for the integral to make any sense
    $endgroup$
    – mathreadler
    Jan 31 '18 at 20:16










2




2




$begingroup$
dont forget the integration symbol dx, you must replace it with some d(new variable) for the integral to make any sense
$endgroup$
– mathreadler
Jan 31 '18 at 20:16






$begingroup$
dont forget the integration symbol dx, you must replace it with some d(new variable) for the integral to make any sense
$endgroup$
– mathreadler
Jan 31 '18 at 20:16












5 Answers
5






active

oldest

votes


















1












$begingroup$

split your integral and write $$sin(x)^3(1-sin(x)^2)=sin(x)^3-sin(x)^5$$
furthere use that $$sin(x)^3=frac{1}{4} (3 sin (x)-sin (3 x))$$
and $$sin(x)^5=frac{1}{16} (10 sin (x)-5 sin (3 x)+sin (5 x))$$






share|cite|improve this answer









$endgroup$





















    2












    $begingroup$


    $$int sin ^{ 3 }{ x } cos ^{ 2 }{ x } dx=-int { sin ^{ 2 }{ x } cos ^{ 2 }{ x } dleft( cos { x } right) } =\ =-int { left( 1-cos ^{ 2 }{ x } right) cos ^{ 2 }{ x } dleft( cos { x } right) } =int { cos ^{ 4 }{ x } -cos ^{ 2 }{ x } dleft( cos { x } right) } =\ =frac { cos ^{ 5 }{ x } }{ 5 } -frac { cos ^{ 3 }{ x } }{ 3 } +C$$







    share|cite|improve this answer









    $endgroup$





















      1












      $begingroup$

      $$intsin^3xcos^2xdx=frac{sin^4x}{4}cdotcos{x}-frac{1}{4}intsin^4x(-sin{x})dx=$$
      $$=frac{sin^4x}{4}cdotcos{x}-frac{1}{4}int(1-cos^2x)^2d(cos{x})=$$
      $$=frac{sin^4xcos{x}}{4}-frac{cos{x}}{4}+frac{cos^3x}{6}-frac{cos^5x}{20}+C.$$






      share|cite|improve this answer









      $endgroup$





















        1












        $begingroup$

        Since you acknowledge that you can do this with more straightforward substitutions, but are curious about parts, let's show that in can be done with parts.



        $int sin^3x cos^2 x dx$



        pick something easy to integrate to be $v'$



        $v' = sin xcos^2 x$ or $v' = sin^3xcos x$ would be my suggestions.



        lets go with the first one.



        $u = sin^2 x, dv = sin xcos^2 x dx\
        du = 2sin xcos x dx, v = -frac 13 cos^3x$



        $-frac 13 cos^3 xsin^2 x + frac 23 int cos^4 xsin x dx\
        -frac 13 cos^3 xsin^2 x - frac 2{15} cos^5 x\
        frac 15cos^5 x - frac 13 cos^3 x$






        share|cite|improve this answer









        $endgroup$





















          0












          $begingroup$

          Integration by parts is unnecessary. Do this
          $$int sin^3(x)cos^2(x),dx = int (1-cos^2(x))cos^2(x)sin(x),dx $$
          Let $u = cos(x), du = -sin(x),dx$ and this resolves very simply.






          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%2f2630232%2fhow-to-solve-int-sin3x-cos2x-dx-with-integration-by-parts%23new-answer', 'question_page');
            }
            );

            Post as a guest















            Required, but never shown

























            5 Answers
            5






            active

            oldest

            votes








            5 Answers
            5






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            1












            $begingroup$

            split your integral and write $$sin(x)^3(1-sin(x)^2)=sin(x)^3-sin(x)^5$$
            furthere use that $$sin(x)^3=frac{1}{4} (3 sin (x)-sin (3 x))$$
            and $$sin(x)^5=frac{1}{16} (10 sin (x)-5 sin (3 x)+sin (5 x))$$






            share|cite|improve this answer









            $endgroup$


















              1












              $begingroup$

              split your integral and write $$sin(x)^3(1-sin(x)^2)=sin(x)^3-sin(x)^5$$
              furthere use that $$sin(x)^3=frac{1}{4} (3 sin (x)-sin (3 x))$$
              and $$sin(x)^5=frac{1}{16} (10 sin (x)-5 sin (3 x)+sin (5 x))$$






              share|cite|improve this answer









              $endgroup$
















                1












                1








                1





                $begingroup$

                split your integral and write $$sin(x)^3(1-sin(x)^2)=sin(x)^3-sin(x)^5$$
                furthere use that $$sin(x)^3=frac{1}{4} (3 sin (x)-sin (3 x))$$
                and $$sin(x)^5=frac{1}{16} (10 sin (x)-5 sin (3 x)+sin (5 x))$$






                share|cite|improve this answer









                $endgroup$



                split your integral and write $$sin(x)^3(1-sin(x)^2)=sin(x)^3-sin(x)^5$$
                furthere use that $$sin(x)^3=frac{1}{4} (3 sin (x)-sin (3 x))$$
                and $$sin(x)^5=frac{1}{16} (10 sin (x)-5 sin (3 x)+sin (5 x))$$







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Jan 31 '18 at 20:14









                Dr. Sonnhard GraubnerDr. Sonnhard Graubner

                75k42865




                75k42865























                    2












                    $begingroup$


                    $$int sin ^{ 3 }{ x } cos ^{ 2 }{ x } dx=-int { sin ^{ 2 }{ x } cos ^{ 2 }{ x } dleft( cos { x } right) } =\ =-int { left( 1-cos ^{ 2 }{ x } right) cos ^{ 2 }{ x } dleft( cos { x } right) } =int { cos ^{ 4 }{ x } -cos ^{ 2 }{ x } dleft( cos { x } right) } =\ =frac { cos ^{ 5 }{ x } }{ 5 } -frac { cos ^{ 3 }{ x } }{ 3 } +C$$







                    share|cite|improve this answer









                    $endgroup$


















                      2












                      $begingroup$


                      $$int sin ^{ 3 }{ x } cos ^{ 2 }{ x } dx=-int { sin ^{ 2 }{ x } cos ^{ 2 }{ x } dleft( cos { x } right) } =\ =-int { left( 1-cos ^{ 2 }{ x } right) cos ^{ 2 }{ x } dleft( cos { x } right) } =int { cos ^{ 4 }{ x } -cos ^{ 2 }{ x } dleft( cos { x } right) } =\ =frac { cos ^{ 5 }{ x } }{ 5 } -frac { cos ^{ 3 }{ x } }{ 3 } +C$$







                      share|cite|improve this answer









                      $endgroup$
















                        2












                        2








                        2





                        $begingroup$


                        $$int sin ^{ 3 }{ x } cos ^{ 2 }{ x } dx=-int { sin ^{ 2 }{ x } cos ^{ 2 }{ x } dleft( cos { x } right) } =\ =-int { left( 1-cos ^{ 2 }{ x } right) cos ^{ 2 }{ x } dleft( cos { x } right) } =int { cos ^{ 4 }{ x } -cos ^{ 2 }{ x } dleft( cos { x } right) } =\ =frac { cos ^{ 5 }{ x } }{ 5 } -frac { cos ^{ 3 }{ x } }{ 3 } +C$$







                        share|cite|improve this answer









                        $endgroup$




                        $$int sin ^{ 3 }{ x } cos ^{ 2 }{ x } dx=-int { sin ^{ 2 }{ x } cos ^{ 2 }{ x } dleft( cos { x } right) } =\ =-int { left( 1-cos ^{ 2 }{ x } right) cos ^{ 2 }{ x } dleft( cos { x } right) } =int { cos ^{ 4 }{ x } -cos ^{ 2 }{ x } dleft( cos { x } right) } =\ =frac { cos ^{ 5 }{ x } }{ 5 } -frac { cos ^{ 3 }{ x } }{ 3 } +C$$








                        share|cite|improve this answer












                        share|cite|improve this answer



                        share|cite|improve this answer










                        answered Jan 31 '18 at 20:15









                        haqnaturalhaqnatural

                        20.6k72457




                        20.6k72457























                            1












                            $begingroup$

                            $$intsin^3xcos^2xdx=frac{sin^4x}{4}cdotcos{x}-frac{1}{4}intsin^4x(-sin{x})dx=$$
                            $$=frac{sin^4x}{4}cdotcos{x}-frac{1}{4}int(1-cos^2x)^2d(cos{x})=$$
                            $$=frac{sin^4xcos{x}}{4}-frac{cos{x}}{4}+frac{cos^3x}{6}-frac{cos^5x}{20}+C.$$






                            share|cite|improve this answer









                            $endgroup$


















                              1












                              $begingroup$

                              $$intsin^3xcos^2xdx=frac{sin^4x}{4}cdotcos{x}-frac{1}{4}intsin^4x(-sin{x})dx=$$
                              $$=frac{sin^4x}{4}cdotcos{x}-frac{1}{4}int(1-cos^2x)^2d(cos{x})=$$
                              $$=frac{sin^4xcos{x}}{4}-frac{cos{x}}{4}+frac{cos^3x}{6}-frac{cos^5x}{20}+C.$$






                              share|cite|improve this answer









                              $endgroup$
















                                1












                                1








                                1





                                $begingroup$

                                $$intsin^3xcos^2xdx=frac{sin^4x}{4}cdotcos{x}-frac{1}{4}intsin^4x(-sin{x})dx=$$
                                $$=frac{sin^4x}{4}cdotcos{x}-frac{1}{4}int(1-cos^2x)^2d(cos{x})=$$
                                $$=frac{sin^4xcos{x}}{4}-frac{cos{x}}{4}+frac{cos^3x}{6}-frac{cos^5x}{20}+C.$$






                                share|cite|improve this answer









                                $endgroup$



                                $$intsin^3xcos^2xdx=frac{sin^4x}{4}cdotcos{x}-frac{1}{4}intsin^4x(-sin{x})dx=$$
                                $$=frac{sin^4x}{4}cdotcos{x}-frac{1}{4}int(1-cos^2x)^2d(cos{x})=$$
                                $$=frac{sin^4xcos{x}}{4}-frac{cos{x}}{4}+frac{cos^3x}{6}-frac{cos^5x}{20}+C.$$







                                share|cite|improve this answer












                                share|cite|improve this answer



                                share|cite|improve this answer










                                answered Jan 31 '18 at 20:17









                                Michael RozenbergMichael Rozenberg

                                102k1791195




                                102k1791195























                                    1












                                    $begingroup$

                                    Since you acknowledge that you can do this with more straightforward substitutions, but are curious about parts, let's show that in can be done with parts.



                                    $int sin^3x cos^2 x dx$



                                    pick something easy to integrate to be $v'$



                                    $v' = sin xcos^2 x$ or $v' = sin^3xcos x$ would be my suggestions.



                                    lets go with the first one.



                                    $u = sin^2 x, dv = sin xcos^2 x dx\
                                    du = 2sin xcos x dx, v = -frac 13 cos^3x$



                                    $-frac 13 cos^3 xsin^2 x + frac 23 int cos^4 xsin x dx\
                                    -frac 13 cos^3 xsin^2 x - frac 2{15} cos^5 x\
                                    frac 15cos^5 x - frac 13 cos^3 x$






                                    share|cite|improve this answer









                                    $endgroup$


















                                      1












                                      $begingroup$

                                      Since you acknowledge that you can do this with more straightforward substitutions, but are curious about parts, let's show that in can be done with parts.



                                      $int sin^3x cos^2 x dx$



                                      pick something easy to integrate to be $v'$



                                      $v' = sin xcos^2 x$ or $v' = sin^3xcos x$ would be my suggestions.



                                      lets go with the first one.



                                      $u = sin^2 x, dv = sin xcos^2 x dx\
                                      du = 2sin xcos x dx, v = -frac 13 cos^3x$



                                      $-frac 13 cos^3 xsin^2 x + frac 23 int cos^4 xsin x dx\
                                      -frac 13 cos^3 xsin^2 x - frac 2{15} cos^5 x\
                                      frac 15cos^5 x - frac 13 cos^3 x$






                                      share|cite|improve this answer









                                      $endgroup$
















                                        1












                                        1








                                        1





                                        $begingroup$

                                        Since you acknowledge that you can do this with more straightforward substitutions, but are curious about parts, let's show that in can be done with parts.



                                        $int sin^3x cos^2 x dx$



                                        pick something easy to integrate to be $v'$



                                        $v' = sin xcos^2 x$ or $v' = sin^3xcos x$ would be my suggestions.



                                        lets go with the first one.



                                        $u = sin^2 x, dv = sin xcos^2 x dx\
                                        du = 2sin xcos x dx, v = -frac 13 cos^3x$



                                        $-frac 13 cos^3 xsin^2 x + frac 23 int cos^4 xsin x dx\
                                        -frac 13 cos^3 xsin^2 x - frac 2{15} cos^5 x\
                                        frac 15cos^5 x - frac 13 cos^3 x$






                                        share|cite|improve this answer









                                        $endgroup$



                                        Since you acknowledge that you can do this with more straightforward substitutions, but are curious about parts, let's show that in can be done with parts.



                                        $int sin^3x cos^2 x dx$



                                        pick something easy to integrate to be $v'$



                                        $v' = sin xcos^2 x$ or $v' = sin^3xcos x$ would be my suggestions.



                                        lets go with the first one.



                                        $u = sin^2 x, dv = sin xcos^2 x dx\
                                        du = 2sin xcos x dx, v = -frac 13 cos^3x$



                                        $-frac 13 cos^3 xsin^2 x + frac 23 int cos^4 xsin x dx\
                                        -frac 13 cos^3 xsin^2 x - frac 2{15} cos^5 x\
                                        frac 15cos^5 x - frac 13 cos^3 x$







                                        share|cite|improve this answer












                                        share|cite|improve this answer



                                        share|cite|improve this answer










                                        answered Dec 12 '18 at 22:09









                                        Doug MDoug M

                                        44.8k31854




                                        44.8k31854























                                            0












                                            $begingroup$

                                            Integration by parts is unnecessary. Do this
                                            $$int sin^3(x)cos^2(x),dx = int (1-cos^2(x))cos^2(x)sin(x),dx $$
                                            Let $u = cos(x), du = -sin(x),dx$ and this resolves very simply.






                                            share|cite|improve this answer









                                            $endgroup$


















                                              0












                                              $begingroup$

                                              Integration by parts is unnecessary. Do this
                                              $$int sin^3(x)cos^2(x),dx = int (1-cos^2(x))cos^2(x)sin(x),dx $$
                                              Let $u = cos(x), du = -sin(x),dx$ and this resolves very simply.






                                              share|cite|improve this answer









                                              $endgroup$
















                                                0












                                                0








                                                0





                                                $begingroup$

                                                Integration by parts is unnecessary. Do this
                                                $$int sin^3(x)cos^2(x),dx = int (1-cos^2(x))cos^2(x)sin(x),dx $$
                                                Let $u = cos(x), du = -sin(x),dx$ and this resolves very simply.






                                                share|cite|improve this answer









                                                $endgroup$



                                                Integration by parts is unnecessary. Do this
                                                $$int sin^3(x)cos^2(x),dx = int (1-cos^2(x))cos^2(x)sin(x),dx $$
                                                Let $u = cos(x), du = -sin(x),dx$ and this resolves very simply.







                                                share|cite|improve this answer












                                                share|cite|improve this answer



                                                share|cite|improve this answer










                                                answered Dec 12 '18 at 21:52









                                                ncmathsadistncmathsadist

                                                42.8k260103




                                                42.8k260103






























                                                    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%2f2630232%2fhow-to-solve-int-sin3x-cos2x-dx-with-integration-by-parts%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

                                                    Wiesbaden

                                                    Marschland

                                                    Dieringhausen