Copyright © University of Cambridge. All rights reserved.

'Weekly Challenge 21: Trig Identity' printed from

Show menu

In this diagram $O$ is the centre of a unit circle. Use it to find a trigonometrical relationship between $A$ and $2A$.
Did you know ... ?

Trigonometrical expressions can often be derived algebraically or geometrically. In more advanced applications the functions of trigonometry are defined as infinite power series rather than geometric ratios.