D shows the circumference. This is the perimeter of the circle, the distance around the shape. Substitute the value of the radius into the formula. Multiply 2 by π then multiply by the radius, ...

Pi, a mathematical constant denoted by the Greek letter π, is the ratio of a circle's circumference C to its diameter d: π = C/d. The circumference of a circle is, in turn, equal to 2πr ...

Simply put, Pi is a mathematical constant that expresses the ratio of a circle’s circumference to its diameter. It is part of ...