Sine Wave 1 - The Unit Circle

Observe the circle to the left of the above diagram. It is of radius one. The blue triangle within the circle has a hypotenuse that is the same length as the radius of the circle and therefore has a length of one.

Observe the graph to the right of the circle. This graph plots the value of the angle in the blue triangle closest to the centre of the circle against the length of the side of the blue triangle that is opposite that angle. The the graph is called a sine wave.

Observe that the green line and the hypotenuse of the blue triangle move at a constant speed. (The green line has linear motion and the blue hypotenuse has angular motion).

Observe that the red line does not move at constant speed. Instead it tends to slow down before it stops at the top and the bottom of each stroke. It reaches maximum speed through the middle of its stroke.

Can you think of something in real life that has motion a bit like the red line? Proceed to Sine Wave Tutorial 2