where n is the number of sides, or angles, in the polygon. This formula is easily
derived from known facts.The sum of the angles in a triangle is 180°; in a rectangle,
360°; and in a pentagon, 540°.Thus, each side added to the three required for
a triangle increases the sum of the angles by 180°. As was mentioned in Section
7.3, if the direction about a traverse is clockwise when observing angles to
the right, exterior angles will be observed. In this case, the sum of the exterior
angles will be