Question

isnt a circle like a rectangle with one side being "r" and another being "pi-r"?

Answer 1

Yes.

Answer 2

I don't think circles and rectangles are related to each other, I could be wrong here although I have never heard of this case being true math..

Answer 3

more like a triangle ... with one side 2 pi r and height r
http://mathworld.wolfram.com/images/eps-gif/CircleAreaStrips_1000.gif

Answer 4

what would r represent in this case?

Answer 5

if it is some arbitrary length, then a rectangle with sides r and pi*r would merely have the same area as a circle of that radius r
I think the relation is rather trivial personally...