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Math Help - Trig Integration Problem - # 3

  1. #1
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    Trig Integration Problem - # 3

    Using Integration by parts \int udv = uv - \int vdu

    \int e^{8\theta} \sin(9\theta) d\theta

    u = \sin(9\theta)

    dv = e^{8\theta}

    v = \dfrac{1}{8}e^{8\theta}

    du = \dfrac{1}{9}\cos(9\theta)

    [\sin(9\theta)][\dfrac{1}{8}e^{8\theta}] - \int[\dfrac{1}{8}e^{8\theta}][\dfrac{1}{9}\cos(9\theta)]

    ?? What is the next step, and are the steps above right? I did try to do integration by parts again, but it still is an integration by parts situation. In fact, I think it would keep doing that over and over.
    Last edited by Jason76; July 2nd 2014 at 10:34 PM.
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  2. #2
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    Re: Trig Integration Problem - # 3

    If u = \sin(9 \theta), then du = 9 \cos(9 \theta)
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  3. #3
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    Re: Trig Integration Problem - # 3

    Using Integration by Parts again IS what you do. You should find that you get a multiple of the original integral you're trying to find, which means you can use simple algebra to solve for it...
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