Vertical Angles are Congruent
1. Lines l and m
intersect making four angles, 1. Given
/ 1, /
2, / 3, / 4.
2. / 1 and / 2, / 1 and / 4 are linear pairs. 2. Definition of linear pair.
3. / 1 and / 2, / 1 and / 4 are supplementary. 3. Definition of linear pair.
4. / 2 and / 4 are vertical angles. 4. Definition of vertical angles.
5. / 2 = / 4 5. Supplements of the same angle
are congruent.