Cosine graph from the Unit Circle

Author:
Mike Day
How does a cosine curve come from a unit circle? Click on Start to watch a point moving around the unit circle. Watch how the length af the triangle (Cosine) is graphed with respect to the angle. Click on Pause to stop at any point. You can show the trace or remove it. What happens to the graph?
When will the graph cross the x-axis? How is this graph different from the sin graph? What is one period for this graph?