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Math Help - Area of a torus

  1. #1
    Junior Member
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    Nov 2009
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    Area of a torus

    The circle x = a cost, y = a sin(t), 0 ≤ t ≤ 2π is revolved about the line x = b, 0 < a < b, thus generating a torus (doughnut). Find its surface area.
    Area of the torus:

    The formula I found for this is :
    S= π^2(R+r)(R-r)^2

    But what is R and r ? What do I need to do to find those?
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  2. #2
    Super Member
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    Aug 2008
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    Hi. Wolfram Mathworld does such a nice job explaining this. Just look up torus and in 2 minutes you'll have it as well as the satisfaction of discovering it for yourself. Give it a try.
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