1. Parallel and Perpendicular Lines
Math 2 - Lesson 13
Mr. Lopez

2. I’m not even going to say it…
Given: a || b and 1 = 4
Prove: c || d a b 2 3 4 c 1 d

3. More About Parallel Lines
If two lines are parallel to the same line, then they are parallel to each other
Ex:
If a || b and b || c then a || c. a b c

4. Perpendicular Lines
Two lines that intersect and form right angles. The symbol for perpendicular lines is 
Ex:
Given: a  b
Therefore, 1 and 2 are right angles a 2 1 b

5. Perpendicular Lines and Parallel Lines
If two lines are perpendicular to the same line then they are parallel to each other
Ex:
Given: t is  to a and b
Therefore, a || b t a b

6. Proof of the perpendicular lines and parallel lines theorem
Given: r  t, s  t
Prove: r || s t 2 r 1 s

7. Oh…One more thing about  and || lines
If a line is  to one of the two || lines, then it is  to the other line.
Ex:
Given: t  a, a || b
Therefore, t  b t a b

8. Proof using the  and one of the two || lines theorem
Given: a  b, b  c, b || d, and c  d
Prove: a  d a c 1 2 b 3 4 d