1. 3-7 Perpendicular Lines

2. Lines that intersect at an angle of 90 degrees are perpendicular lines. For example, let’s say that we have the and the line ABline CD A B CD Now, if the lines intersect at an angle of 90 o, then AB  CD.

3. Definition of Perpendicular Lines Perpendicular lines are lines that intersect to form a right angle. m n Symbols: m  n

4. m n 1 2 34

5. Theorem 3-8 If two lines are perpendicular, a b Symbols: a  b then they form 4 right angles. 12 34

6. R In the figure, P O M N OP  MNNP  QS. and Q S Determine whether each of the following is true or false. 1 2 False. True. Since OP  MN, are vertical angles, and vertical angles are congruent. 3 4 QR  PR 1 2 3 4 5 6 7 8 False. True.If two lines are perpendicular, then they form 4 right angles.