Lissajous curve

The path of a point moving with two sine motions at right angles, x = sin(at + δ) and y = sin(bt). When a/b is a ratio of whole numbers the curve closes; when it is irrational the curve never closes and fills its rectangle. On an oscilloscope, two signals fed to x and y draw it, and its shape shows the difference in their phase.

x = A sin(at + δ), y = B sin(bt)

On mathcurve.com as Courbe de Lissajous