That depends on what information you have to begin with.
The following relations apply to circles:
\(area = \pi * r^2\)
\(circumference = 2*\pi*r\)
In which the Greek letter pi is simply a number, approximately 22/7 but in reality 3,1415... endless string of numbers.
The meaning of this number is as such. If you have a radius then there is a specific angle at which the length of the described arc is equal to the radius. This angle is defined as one radian. The number of radians that fit in one circle, or 360 degrees, is exactly 2 pi radians. Therefore the circumference becomes 2 * pi * r.
If you know the radius of the circle, or the diameter, which is twice the radius (note D = 2*r) you can easily compute the circumference.
If you have the area of a circle, you can divide by pi and take the square root:
\(r=\sqrt{area\over\pi}\)
From which you can then calculate the circumference.
how do you solve the circumference of a circle?►
