Interestingly enough,
Π is also the ratio between the area of a circle and the square of its radius. Thus,
Π = A/r2;
A = Π×r2; and
r = 
. The most important equation to remember is the middle
equation,
A = Π×r2. Thus, to find the area of a circle,
square the radius and multiply by
Π. If the radius is unknown but the
diameter is known, divide the diameter by 2 to find the radius.