I was wondering if it was possible (just out of curiosity) to show that the circumference of a unit-circle is 2(pi) WITHOUT using the rule C = 2(pi)r? Is it possible to take a unit-sphere (a sphere with r=1) and triple integrate it. Something like... SSS sqrt(x^2 + y^2 + z^2)dxdydz = 2(pi) I thought this might be an interesting little problem. Anyone more than welcome to add to the calculation. Any help would be great too! I'll post back with anything I can find. Cheers.