You can put this solution on YOUR website! The ratio of a circle's circumference to its diameter. It is expressed using the Greek lowercase letter pi (). The numerical value is roughly 3.141592653589...; it is irrational and transcendental. Pi is a really interesting number, because it can appear anywhere in math, not just in problems involving circles.
Here is the Wikipedia article on pi:
http://en.wikipedia.org/wiki/Pi
