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Math Help - Integral prob

  1. #1
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    Integral prob

    Integrate y^2 cos3y
    I though of using product rule
    1/3sin3y y^2 - integral of 1/3sin3y 2y
    it looks quite complicated already.
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  2. #2
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    Quote Originally Posted by kandyfloss View Post
    Integrate y^2 cos3y
    I though of using product rule
    1/3sin3y y^2 - integral of 1/3sin3y 2y
    it looks quite complicated already.
    Use integration by parts - twice. (Assuming you have correctly used it once, the remaining integral is obviously simpler. One more integration by parts and the remaining integral will be trivial).
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  3. #3
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    And, yes, what you have is simpler, not more complicated. Before you had y^2 multiplying the trig function, now only "y". One more integration by parts should remove that "y" entirely.
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