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Math Help - Problems with an Integral

  1. #1
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    Problems with an Integral

    \int x^2 cos(mx) dx

    I have trouble solving this. I know that i have to integrate by parts, but somehow i always get the wrong answer.... I put it into Wolframalpha, but im having a hard time following its solution

    any help would be appreciated
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  2. #2
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    Quote Originally Posted by coobe View Post
    \int x^2 cos(mx) dx

    I have trouble solving this. I know that i have to integrate by parts, but somehow i always get the wrong answer.... I put it into Wolframalpha, but im having a hard time following its solution

    any help would be appreciated
    tabular integration ...

    Code:
    .............. u ........... dv
    
    + .............x^2 ........ cos(mx)
    
    - ............ 2x ..........(1/m)sin(mx)
    
    + ............. 2 ......... -(1/m^2)cos(mx)
    
    - ............. 0 ...........-(1/m^3)sin(mx) 
    \textcolor{red}{\frac{x^2}{m} \sin(mx)} + \textcolor{green}{\frac{2x}{m^2}\cos(mx)} \textcolor{blue}{- \frac{2}{m^3}\sin(mx)} + C
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