Sine Graph -- Radians

In this sketch, a circle is superimposed over a sine graph. This sine graph is controlled by two parameters: the center of the circle, and the radius of the circle (the r slider on the left). A point controlling another parameter -- an arc length -- is also provided; moving this point causes another point on the sine graph to also move. These two points are identical in terms of the green distance highlighted on the circle and on the x-axis.