Pappus' Theorem (surface area)

1. Feb 8, 2013

whatlifeforme

1. The problem statement, all variables and given/known data
Use Pappus' Theorem for surface area and the fact that the surface area of a sphere of radius c is 4(pi)c^2 to find the centroid of the semicircle x= sqrt ( c^2 - y^2)

2. Relevant equations
S = 2 (pi) * p * L

where s=surface area; p=distance from axis of revolution; L= length of the arc

3. The attempt at a solution
1. centroid of semicircle. should i put the equation in circle form, and attempt to solve from that?

2. Feb 8, 2013

Dick

No, you don't. You need to think about what that equation means and how it's related to what you want to find. It's almost all you need to know.

3. Feb 9, 2013

whatlifeforme

i'm still lost.

4. Feb 9, 2013

Dick

Explain to me what the variables in that equation mean. Yes, S=surface area. But surface area of WHAT? Look it up if you don't have a good reference handy.

5. Feb 11, 2013

whatlifeforme

S = 2 (pi) * p * L

where s=surface area; p=distance from axis of revolution; L= length of the arc

6. Feb 11, 2013