Regular Polygon

A regular polygon is a polygon where all the sides are the same length. Polygons don't have to be 'regular'. Here is a regular hexagon (a 6-sided polygon) along with 2 irregular ones for comparison:

For a regular polygon, the interior angles (the angle adjacent sides make with each other) are all the same. Here is the formula for computing what that angle is:
A = 180 x (N - 2)
N Where N is the number of sides of the regular polygon.
So, for a equilateral triangle, A = (180 x 1) / 3 = 60^o
For a hexagon, A = (180 x 4) / 6 = 120^o