C2 Topic 4: Trigonometry
From circle to graph
As a point is moved round a unit circle, a graph of the trigonometrical function can be produced. Click Start to see the graph of the sine function being drawn from the unit circle definition. This graph is called a sine wave.
The cosine wave can be produced in the same way.
The tangent wave has very different characteristics.
The shape of the tangent graph must be clearly understood. The above graph shows spikes every 180°. This is misleading. To be precise, the graph is undefined at these points. The display below should make this clear.

Summary Trigonometry applets from catcode.com and W.Fendt