Equation of a circle

A complete lesson on the equation of a circle with centre the origin. The intention is to get pupils familiar with not only the format of the equation of a circle, and a derivation of the equation, but also problems involving coordinates on a circle.

Activities included:

Starter:
A related question where pupils try to identify which of three given points are closer to the origin, before considering what must be true if points are a given distance from the origin.

Main:

• The starter leads directly into a clear definition of the equation of a circle, followed by a set of quick diagnostic whole-class questions to check for understanding.
• Example-question pairs of increasingly difficult problems involving coordinates on circles, followed by a set of three worksheets. The last one is more of a mini-investigation, with opportunities for pupils to conjecture and generalise.

Plenary:
Three final puzzles to check for understanding.

Printable worksheets and answers included.

Please review if you buy as any feedback is appreciated!