Alternate Exterior Angles

Then one of the alternate angles is an exterior angle equal to the other angle which is an opposite interior angle in the triangle.

Regular Polygon

a regular polygon is a polygon that is equiangular (all angles are equal in measure) and equilateral (all sides have the same length). Regular polygons may be convex or star. In the limit, a sequence of regular polygons with an increasing number of sides becomes a circle.

Transversal

A line that intersects two or more parallel lines.