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Surface Area of a Frustum

  1. Nov 1, 2011 #1


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    Ok, so I have problems understanding where they came up with the formula
    S=2∏rL, where r = (1/2)(r1+r2).

    They say the formula is verified in exercise 62. I did the exercise and showed that S=∏rL.

    Correct me if I'm wrong, but isn't this contradictory? I can see how they're using the average radius of the frustum, but I'm not sure what allows them to do that. I guess I just need to see a geometric proof before I really get it.


    Any ideas? Thanks in advance.
  2. jcsd
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