Angle Proof Reference

Definition of congruence

The measures of two angles are equal if and only if the angles are congruent

Definition of a right angle

An angle measures 90 degrees if and only if it is a right angle

Definition of complementary angles

Two angles are complementary if and only if the sum of their measures is 90 degrees 

Definition of supplementary angles

Two angles are supplementary if and only if the sum of their measures is 180 degrees 

Definition of an angle bisector

An angle bisector divides an angle into two equal parts

Definition of perpendicular

perpendicular lines form right angles (upside down T)

Angle Addition postulate

m<ABD + m<DBC = m<ABC

Vertical angles theorem

If two angles are vertical, then they are congruent

Complement Theorem

If two angles form a right angle, then they are complementary

Linear Pair theorem (supplement theorem)

If two angles form a linear pair, then they are supplementary