The formula for the area, a, of a regular polygon in terms of the perimeter of the polygon, p, and the length of the apothem, a, is: img2 upper a = one-half a p. a polygon with 5 sides has an apothem with measure a. what is the equivalent equation when solving for p? p = one-half upper a a p = startfraction 2 upper a over a endfraction p = 2 upper a a p = startfraction upper a over 2 a endfraction