Alternate Interior Angles

congruent angles created by parallel

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.

acute triangle

A triangle where all three internal angles are acute (less than 90 degrees).

altitude (of a triangle)

The definition of the altitude of a triangle is a line that extends from one vertex of a triangle perpendicular to the opposite side.

cpctc

Corresponding Parts of Congruent Triangles are Congruent