archimedes, pi is the name of the greek letter p, which was used as the shortened version of the greek word perimeter,or circumference of a circle. archimedes was looking for a formula to find the area of a circle, and he required a more accurate value for the constant pi. previously pi had been assigned a very approximate value of 1/3 or 22/7.
I don't think it was the same person. And there are several formulae to determine pi; which one do you mean?
4/3 pi r^3
The value of pi is the circumference of a circle divided by its diameter
V = radius2 x Pi x length