Postulate: Angle Addition Postulate

Point B lies in the interior of ? XYZ, if and only if, m?XYB + m?BYZ = m?XYZ 

Like the Segment Addition Postulate, the Angle Addition Postulate is often used in geometric proofs when an arbitrary point is designated on the geometric figure in question, to facilitate the formulation of the required proof.

Complementary Angles are two angles whose measures sum up to 90°. The angles are complement of each other.

Supplementary Angles are two angles whose measures sum up to 180°. The angles are supplement of each other.

Congruent angles are angles that have equal measure.

Adjacent angles are two coplanar angles having a common vertex and a common side, but no common interior points.