This demo displays the circle given by X(t) = (a,b) + (Rcos(t), Rsin(t)).
(a,b), click and drag on the point labeled "(a,b)". To change R, click and drag the point
labeled "R". To move the
point X(t0) along 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", "Show position
vector X(t0)", and "Show Color Spectrum" options.