Chapter 21: Circle geometry and circle theorems

The chapter problem

A circular window has a straight line across it, from one edge to another. This chord is $13$ cm long, and the radius is $7$ cm. Predict whether the chord could fit in the window. Give one reason for your prediction.

By the end of this chapter you will be able to

• name and use the centre, radius, chord, diameter, circumference, tangent, arc, sector and segment;

Route through the chapter

1. 21.1 Parts of a circle introduces the language and parts of a circle.

Make a connection

Circles appear in a wheel, a round window, a clock, and many other designs. Choose one example that matters to you or someone you know. Write one sentence explaining where a circle fact from this chapter could help.