Expressions for the geodesic curvature and speed of a function
may be entered in the control window. The speed function is
defined by f(t), and the geodesic curvature is defined by g(t).
A plot of f(t) against t is displayed in the f(t) window.
A plot of g(t) against t is displayed in the g(t) window.
The curve defined by these geodesic curvature and speed functions
is displayed in the Curve: X(t) window. The curve originates at
the origin in the direction of the positive x-axis. The curve is
displayed for values of t from 0 to t0. The value of t0 may be
changed in the control window.