Question

Please define the Volume Theorem. Or give me a link that would explain to me about it. I can't find any :(

Answer 1

http://mathworld.wolfram.com/VolumeTheorem.html

Answer 2

Read the definition that pratu just linked to.

Now consider the example of a cylinder.

The volume lied between two parallel planes, the top and bottom surfaces have equal area, every section between the two is of equal area, pi.r^2 where r is the radius of the circle, and then indeed the volume V of the object overall is just the
V = (area of base) x (altitude between the planes)
= pi.r^2 h