A Lissajous curve is a parametric curve in dimension 2, described by a pair
of functions

x = cos(nt) , y = sin(mt+a) .

These curves occur often in the study of electronics. They form a good
example of parametric curves.

This online exercise can either plot a Lissajous curve and ask you to recognize its
equations among a list to choose from, or give a pair of equations
and ask you to recognize the plotted Lissajous curve among a list to choose from.