Circle perimeter

Perimeter is the distance around a two-dimensional shape.

Circle — is a part of a plane lying inside a circle. In other words, this is the geometrical location of the points of the plane, the distance from which to a given point, called the center of the circle, does not exceed a given non-negative number. The number is called the radius of this circle. If the radius is zero, then the circle degenerates to a point.

The perimeter of a circle is equal to the product of the radius by two pi (3.1415) or if we have the diameter P=pi*D.