Here are four movies showing rotating phasors and
how the real part of the phasor traces out a sinusoid
Two of the movies show how rotating phasors of
different frequencies interact to produce complicated
waveforms such as beat signals.
Sine Drill (sindrill) is a program that tests the users ability to determine
basic parameters of a sinusoid.
After a plot of a sinusoid is displayed, the user must correctly
guess its amplitude, frequency, and phase.
ZDrill is a program that tests the users ability to calculate the result
of simple operations on complex numbers.
The program emphasizes the vectorial view of a complex number.
The following six operations are supported: