Note 2

Note that the angle of rotation, which is equal to the external angle, is also equal to the central angle of the polygon. For regular polygons, the central angle has its vertex at the center of the polygon, and its rays go through any two adjacent vertices. In Session 4, we defined central angles in terms of circles. Here, you can think of circumscribing a circle about the regular polygon. Then these two notions of central angle coincide.

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