Definition of right angle Reasons Definition of straight angle Definition of linear pair Definition of perpendicular lines **Once you have proven a theorem, it can be used in any later proof as a reason.
Midpoint Theorem If M is the midpoint of, then A B M
Supplement Theorem If two angles form a linear pair, then they are supplementary angles.
Angles complementary to the same angle or to congruent angles are congruent. 1 2 3
Vertical Angles Theorem If two angles are vertical angles, then they are congruent. 1 2 3 4
If two angles are congruent and supplementary, then each angle is a right angle.