Curves, which are not determined by an explicit function term, but by two functions for the horizontal and vertical direction, can be plotted with this program.
1. The Circle x(k) = sin(k) y(k) = cos(k) k from Pi to Pi 

2. The Spirale x(k) = k/8*sin(k) y(k) = k/8*cos(k) k from 0 to 20 

3. The Lissajou figures x(k) = sin(3*k) y(k) = cos(5*k) k from Pi to Pi 

Lissajou figures are obtained when two ac voltages with different frequencies are applied to one oscilloscope 