Are you sure you have that right?- you actually want the rotation speed to vary with the sin?
Reason I'm asking is that a point on a circle describes a sine path anyway, in the sense that if you project the point over to a graph on the side, with x-axis as angle, then the y height depends on the angle.
For a constant rotation speed w (lower case omega) , and time t, then: y = sin(wt)
Edit.... ok I typed that while you were posting that pic...