# Deriving the cosine graph from the unit circle

- Author:
- Sam Waterfield

- Topic:
- Circle, Cosine, Unit Circle

**Important convention:**Angles are always measured anticlockwise from the positive x-axis. Drag the angle slider along to see how the cosine graph is generated. Consider how this follows on from the first applet. Why is it useful to use the unit circle (radius 1)? What is the

__amplitude__of the cosine graph? How can you tell by looking at the graph/unit circle? What is the

__period__of the cosine graph? How can you tell by looking at the graph/unit circle?