This demo includes a single graphical window that displays a curve X(t) (which you may change in the appropriate textbox in the control window), the point X(t0), the unit tangent vector T(t0) with base X(t0), the involute curve I(t) = X(t) + (c – s(t))T(t) for parameter c defined in the control window, and, if the "String" box in the control window is checked, a curve showing that one can interpret the involute curve as the result of winding or unwinding a string around the curve X(t) and having the end of the string trace out a curve. The control window lists several curves that you may enter for X(t). For example, type cardioid(t) in the textbox for X(t) to make X(t) a cardioid. The control window also includes parameters used in defining these curves. To change these parameters or t0, use the following buttons:

[<]: Decrease variable by one step.
[>]: Increase variable by one step.
[<<]: Decrease variable until it reaches its minimum value.
[>>]: Increase variable until it reaches its maximum value.