This demo includes two graphical display windows.
The window "Curve: X(t)" displays the curve X(t),
the point X(t0), a point V, its position vector V, and a unit circle
centered at the origin. You can drag the point V along the unit circle
shown in the window.
The window h(t) shows a graph of the height function h(t) = X(t)*V.
You can change t0 and X(t) in the control window. The
control window also includes a list of curves that you can enter for
X(t) and parameters used in defining those curves. For example, enter
cardioid(t) in the X(t) textbox to make X(t) a cardioid. Changing k
will then change the cardioid.