What you see in the Circular to SHM display is the point on the circle as a yellow dot, the projection of the point onto the x axis as a green dot. The line connecting the circulating point to the origin is in yellow and makes an angle
with the x axis. The line from the circulating point perpendicular to the x axis is shown in green. When you click on Action time begins to advance in steps of
t=.02 seconds. The angular frequency
is set to .75 rad/sec. At any instant the angle between the yellow line and the x axis is
*t + . The velocity along the x axis is shown as a green vector attached to the green point which is undergoing the simple harmonic motion. This velocity is calculated as the x component of the velocity of the circulating point, r*, where r is the radius 3.0m. The acceleration of the green point is calculated as the x component of the acceleration of the circulating point, r*^{2}. Acceleration along the x axis is shown as a red vector attached to the green point.