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Homework Help: Volume Question

  1. Nov 24, 2008 #1
    1. The problem statement, all variables and given/known data

    Find the volume enclosed by the torus rho = sin theta.

    2. Relevant equations

    3. The attempt at a solution

    I tried setting the limits as phi from 0 to pi, theta from 0 to 2 pi, and rho from 0 to sin theta. However, if i do that, i get a volume of 0. How should i set up the limits?
  2. jcsd
  3. Nov 24, 2008 #2


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    Which angle is theta? There is more than one convention for spherical coordinates. From your limits I would guess its the azimuthal angle, but from rho=sin(theta) I'd guess its the polar angle. Can you show the integral you finally got?
  4. Nov 24, 2008 #3
    I'm an idiot. It's the azimuthal angle. I tried solving it as the polar angle. Thanks.
  5. Jan 5, 2009 #4
    Solutions for volumes of rotation are easy using the Pappus theorem. This is attributed to Pappus of Alexandria, but was first proved by the Swiss mathematician Guldin. The theorem states that the volume is the area of the profile times the distance that the center of gravity of the profile moves. The axis of rotation cannot pass through the profile.
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