One last thing that has to be discussed when dealing with circles is circumference, or the distance around a circle. The circumference of a circle equals 2 times PI times the measure of the radius. That postulate is usually represented by the following equation (where C represents circumference and r stands for radius): C = 2(PI)r.
For example, if a circle has a radius of 3, the circumference of the circle is 6(PI).
Also, you can find the length of any arc when you know its degree measure and the measure of a radius with the following formula (L = length, n = degree measure of arc, r = radius): L = (n/360)(2(PI)r).