Given the lenth of the legs (the same, since this an isoceles) and the vertex angle (is that redundant..."vertex" and "angle"?), how can I calculate the length of the base? You've probably guessed that geometry isn't my strength -- I'm a potter. I wanted to put 3 feet on a round pot, a friend gave me the number .866 to multipy the diameter in order to get three equally spaced points around the circumference -- it works, but I never found out HOW he got this. Plus, I'm now interested in dividing a round pot into 5 equal parts -- I'm assuming the same aproach would work.