1. Math Humor
Q: How do the geometry teacher and track coach wake up their son?
A: It’s time to rise and run!!!

2. LT 3-5: Find and use the slope of a line to identify parallel and perpendicular lines

3. Review
Slope
Equation of a line
y = mx + b
m = slope
b = y - intercept

4. Review cont. Example 1: Find the slope (m) and y-intercept (b):
a) y = x – 4 b) y = -2x + 3
m = m =
b = b =

5. Review cont.
Example 2:
Graph
y = 2x – 3

6. Use the slope formula to determine the slope of the lines:

8. Slopes of Parallel and Perpendicular Lines
Parallel Lines Theorem – In a coordinate plane, two nonvertical lines are parallel if and only if they have the same slope. Any two vertical lines are parallel.
Perpendicular Lines Theorem – In a coordinate plane, two nonvertical lines are perpendicular if and only if the product of their slopes is -1. Vertical and horizontal lines are perpendicular .

9. Examples:
Find the slope of a line parallel to: 1) 2)

10. Examples:
Find the slope of a line perpendicular to: 3)
4) 2x + y = 25

11. On your whiteboard: Determine whether the lines are parallel, perpendicular or neither.

12. On your whiteboard: Determine whether the lines are parallel, perpendicular or neither.F.

13. On your whiteboard: Determine whether the lines are parallel, perpendicular or neither.G. H. I.

14. On your whiteboard: Determine whether the lines are parallel, perpendicular or neither.J. K. L.

15. Before you leave…
How do you know if two lines are parallel, perpendicular or neither?