### Introduction

A circle is one of the most familiar geometrical figures and has been around a long time! In this brief Section we discuss the basic coordinate geometry of a circle - in particular the basic equation representing a circle in terms of its centre and radius.

#### Prerequisites

• understand what is meant by a function and be able to use functional notation
• be able to plot graphs of functions

#### Learning Outcomes

• obtain the equation of any given circle
• obtain the centre and radius of a circle from its equation