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Math Help - Volume of a revolved curve

  1. #1
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    Volume of a revolved curve

    Find the volume generated by revolving the region between y = sinx from [0,\pi] and the line y = 0 about the x-axis.

    I keep coming up with 0 as an answer, and I know this can't be true. Can someone please tell me what I'm doing wrong?
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  2. #2
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    Quote Originally Posted by penguinpwn View Post
    Find the volume generated by revolving the region between y = sinx from [0,\pi] and the line y = 0 about the x-axis.

    I keep coming up with 0 as an answer, and I know this can't be true. Can someone please tell me what I'm doing wrong?
    Are you using V=\int_0^{\pi}\pi(sin x)^2\,dx?
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  3. #3
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    Yes, I realized that I was integrating sin^2 x wrong, and that I had to use the double angle formula. I came up with \frac{\pi}{2}
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    Quote Originally Posted by penguinpwn View Post
    Yes, I realized that I was integrating sin^2 x wrong, and that I had to use the double angle formula. I came up with \frac{\pi}{2}
    <br />
\int_0^{\pi}(sin x)^2\,dx=\frac{\pi}{2}<br />

    <br />
V=\int_0^{\pi}\pi(sin x)^2\,dx<br />

    Multiply your answer by \pi
    Last edited by ione; March 28th 2010 at 09:37 PM.
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