3-7 Perpendicular Lines

Lines that intersect at an angle of 90 degrees are perpendicular lines.

For example, let’s say that we have the

and theline AB line CDA

B

C D

Now, if the lines intersect at an angle of 90o,

then AB CD.

Definition of Perpendicular

Lines

Perpendicular lines are lines that intersect to form a right angle.

m

n

Symbols: m n

m

n1 2

34

Theorem 3-8

If two lines are perpendicular,

a

b

Symbols: a b

then they form 4 right angles.

1 2

34

R

In the figure,

P

O

M

N

OP MN NP 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

12

3

456

7

8

False.

True. If two lines are perpendicular,then they form 4 right angles.