Unit Circle and Sine Curve

The alpha-value on the unit circle is the x-value for each of the traces for the sine curve and cosine curve. The y-values for each of the traces for the sine curve and cosine curve are the sin(alpha) and cos(alpha). Thus, D= (alpha, sin(alpha) and E= (alpha, cos(alpha)).

Questions:
1. As "c" is dragged around the unit circle, what happens to the traces of the sine curve and cosine curve? (Make sure the check box for each trace has a check mark in it.)
2. Try starting the animation when alpha is greater than 4 radians. Where does the trace start? What does this confirm from the explanation given above the construction?

Janel Warren, 4 November 2013, Created with GeoGebra