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Math Help - [SOLVED] Finding volume with integration

  1. #1
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    [SOLVED] Finding volume with integration

    f(x)=4sinx on (0, pi)
    Find the volume of a 3d-solid obtained by rotating this region about the dashed line y=-1

    I realize this is just like a regular integration volume equation but I'm having trouble distinguishing the radii.

    V= pi (0---pi) (R^2-r^2) dx

    Is r=4 and then R=(f(x)-f(-1))? And how would I write this in the above formula so as to be able to integrate it?

    Thanks in advance!
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  2. #2
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    Quote Originally Posted by yzobel View Post
    f(x)=4sinx on (0, pi)
    Find the volume of a 3d-solid obtained by rotating this region about the dashed line y=-1

    I realize this is just like a regular integration volume equation but I'm having trouble distinguishing the radii.

    V= pi (0---pi) (R^2-r^2) dx

    Is r=4 and then R=(f(x)-f(-1))? And how would I write this in the above formula so as to be able to integrate it?

    Thanks in advance!
    V=\pi\int_{0}^{\pi}R^2dx

    =\pi\int_{0}^{\pi}\left(4Sinx+1\right)^2dx
    Attached Thumbnails Attached Thumbnails [SOLVED] Finding volume with integration-4sinx.jpg  
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