In this tutorial you are shown how the equation of a circle is derived when you know the centre and radius.

Formulae to remember:

  • (x – x1)2 + (y – y1)2 = r2 where the centre has coordinates (x1 , y1) and radius = r2

You will also be taken through this example.


  1. Find the equation of a circle with centre (4, -2) and radius 3.
Cartesian Equation of a Circle | ExamSolutions - youtube Video