Furthermore, since the exterior angle size is
180 - 2ß = 180° - (180° - (360°/n))
= 180°- 180° + (360"/n) = 360°/M,
we see that the exterior angle size is the same as the
central angle size, as we argued in Figure 2.
Another argument can be put forth by students familiar
with corresponding angles and alternate interior angles
formed when parallel lines are cut by a transversal
(Eig. 6, applied to a regular pentagon).
Fig. 6