Parametric Curves
This program can be used to plot curves that are not determined by an explicit function term, but by two functions for the horizontal and vertical direction.
Examples:
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 a-c voltages with different frequencies are applied to an oscilloscope.
See also:
Supported FunctionsSetting the graphics
Wikipedia: Parametric equation | Lissajous curve