Equation of a circle

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-x_1)^2 + (y-y_1)^2 = r^2} \\ \text{where the centre }= (x_1, y_1) \text{ and radius }= r

You will also be taken through this example.


  1. Find the equation of a circle with centre (4, -2) and radius 3.

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