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Math Help - Volumes Of Revolution (Tricky Set-up)

  1. #1
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    Volumes Of Revolution (Tricky Set-up)

    Calculate the volume of the solid obtained by rotating the region between the graphs of y = 1/(x^2 - 3x + 2) and y = 0 for 4 ≤ x ≤ 10 around the y-axis.

    I can't seem to set this up. It's being rotated about the y-axis so the function should be in terms of y, but getting it be in terms of y is impossible.

    What should I do?
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  2. #2
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    Re: Volumes Of Revolution (Tricky Set-up)

    Have you heard of discs vs. cylinders?

    Quote Originally Posted by bhaktir View Post
    It's being rotated about the y-axis so the function should be in terms of y
    ... Only if you are confined to discs (or 'washers')... where you rotate each Riemman strip around the axis perpendicular to the strip, e.g. you rotate a vertical strip (whose top and bottom values are in terms of x) around the x axis. Giving you a disc (in this case, but more generally a washer). Rotate the same vertical strip around the y axis instead and what do you get?

    Solid of revolution - Wikipedia, the free encyclopedia
    Last edited by tom@ballooncalculus; September 13th 2011 at 07:36 AM. Reason: clarity, hopefully
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