Perimeter - Circumference of A Circle

Circumference of A Circle

The perimeter of a circle, often called circumference, is proportional to its diameter. That is to say, there exists a constant number π (the greek p for perimeter) which gives, if P is the circle's perimeter and D its diameter:

P = π D.

If one knows the radius R of the circle, this formula becomes:

P = 2 π R.

To calculate a circle's perimeter, the knowledge of its radius or diameter and of the number π is sufficient. The problem is that π is not rational (it cannot be expressed as the quotient of two integers), nor algebraic (it is not a root of a polynomial equation with rational coefficients). So, obtaining an accurate approximation of π is not easy. The search for the digits of π mobilizes many fields, such as mathematical analysis, algorithmics and computer science.