Sine waves in PostScript
The following images illustrate how the step size can be varied to generate different Bézier approximations. The step size parameter should not be more than pi/2 radians (or you get results like this).
Step = pi/2 radian
Step = pi/3 radian
Step = pi/4 radian
(This approximation should be good enough for most purposes. The PostScript source
for this annotated diagram is here.)
Step = pi/6 radian
As a parting thought, it's possible to get a decent approximation
with a step as large as pi radians, by shifting the phase by pi/2:
(Code for this is here.)