This demo includes a single graphical display window that displays the
curve X(t) = A + x(t)B + y(t)C. By default, it shows a circle of radius
r with x(t) = r*cos(t) and y(t) = r *sin(t). You can change t_{0},
A, B, C, r, x(t), and y(t) and choose whether or not to show
the entire curve and the position vector X(t_{0}) in the
control window.