This demo displays the circle given by X(t) = A + (Rcos(t), Rsin(t)).
A, click and drag on the point labeled "A". To move the
point X(t0) along the circle, or to change R, the radius of
the circle, use the arrow buttons ([<], [>], [<<],
[>>]), which have the same function as in the first two demos. As
in earlier demos, there are "Show entire curve" and "Show position
vector X(t0)" options.