1. Section 2-5 Perpendicular Lines

2. Two lines that intersect to form right angles (90 degrees) Lines that form one right angle ALWAYS form four right angles 1 43 2

3. Definition of perpendicular lines Used in two ways: –Given lines perpendicular to one another, you can conclude that the angles formed are right angles –Given a right angle, you can conclude that the lines are perpendicular

4. Perpendicular can also apply to intersecting rays and segments.

5. Theorems to know! If two lines are perpendicular, then they form congruent adjacent angles. If two lines form congruent adjacent angles, then the lines are perpendicular.

6. Another Theorem: If the exterior sides of two adjacent acute angles are perpendicular, then the angles are complementary. 1 2 Exterior Side Are complementary Are two adjacent acute angles