**Theorem 4.1**: The angle at Pj is 180-360j/n.

The angles at P_{j-1} are 180-360(j-1)/n.

The angle at P_{j-2} is 180-360(j-2)/n.

**proof**: The top angle follows from the fact that is a point
on an {n/j} star, the middle angles are the supplements of the angles
at the points of an {n/j-1} star, and the angle at the bottom is a
vertical angle to an angle at a point on an {n/j-2} star.