Circle in a Geometric Plane

Circle in a Geometric Plane

Two-dimensional figure consisting of the set of all the points that are equally distant from the same point called the centre of the circle.

In this figure :

Notation

Common notations for the circle are d for the diameter, r for the radius and C for the circumference. The letter O refers to the centre of the circle.

Formulas

The formulas used to calculate the circumference C and the area A of a circle are the following :

• $$C = 2π r$$
• $$A = πr^2$$ or $$A = \dfrac{πd^2}{4}$$