# Introduction

**Circle**

A circle is a set of points on a plane which are at a constant distance from a fixed point. The fixed point is known as the centre of the circle.

The radius (r) of a circle is a line segment, with one end point at the centre of the circle, and the other on the circle.

We come across many circular shapes in our daily life such as (i) bangle (ii) one rupee coin (iii) moon (iv) wheel (v) clock

**Circumference and Area of a Circle**

The perimeter (boundary) of a circle is called its circumference. Area of a circle is the space inside the circle.

By initially reviewing the calculation of the perimeter and areas of a circle we shall find the areas of two parts of a circular regions namely the sector and segment of a circle as well as the areas of some combination of plane figures involving circles or their parts.