Geometry help? Involving 3D figures. Will give medal.

Question

anonymous · Answer

I have to give a proof to explain why a rectangle that is rotated about the y axis would be a cylinder

anonymous · Answer

My lesson didn't say anything about proofing this sort of question??

anonymous · Answer

@ recangle looks like cylinder . ????? which chapter  .

anonymous · Answer

..What?

anonymous · Answer

@ganeshie8 do you know how the heck this is supposed to have a proof?

wolfe8 · Answer

Well if you rotate a rectangle along an axis the area you will see is the area covered by the rotation of the furthest distance from the center(vertices), right? And rotations will always result in a circular area when viewed from above. Can you imagine that? I'm not sure how to prove it though. Through drawings would be easiest.