A regular polygon is a polygon where all of the sides are congruent and all of the interior angles are congruent.

a: The length of an apothem of the regular polygon

n: The number of sides of the base of the regular polygon

s: The length of a side of the base of the regular polygon

P: The perimeter of the interior of the regular polygon

A: The area of the interior of the regular polygon

P = ns    (there are "n" sides, each of length "s")