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Homework Help: Surface Area of a Torus

  1. Aug 27, 2012 #1
    So the first question is to find the surface area of a torus generated by rotating the circle (or shall I say semi circle) y=√r-x2 around y=r

    if the idea is to find the surface are of the half torus and then multiply by 2, wouldn't it be the same for the circle (or shall I say semi circle, again) rotated around x=r???

  2. jcsd
  3. Aug 27, 2012 #2


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    No, I don't think so. If you rotate the same semicircle around the two different axes the surfaces look pretty different, don't they? One looks like the upper half of a full torus, the other looks like the inner half of a full torus. Don't think they are equal in area.
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