This demo displays the circle given by X(t) = (a,b) + (Rcos(t), Rsin(t)).
(a,b), type the desired expression for (a,b) in the appropriate text box in the
control window and press Enter. 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", "Show position
vector X(t0)" and "Show Color Spectrum" options.