Regular Polygons

Plots the regular polygon {N/d} with vertices on a circle of radius 'rad'.

Let d < N be a positive integer and define p = N/d. Let y_{1} be a point on the unit circle. Let R be clockwise rotation by the angle t = 2*pi/p. The generalized regular polygon {p} is given by the points y_{i+1} = R * y_{i}, and edges between points i and i+1.

Example:
polygon(9, 4, 1);