1. Slope – Parallel and Perpendicular Lines Mrs. King and Ms. Reed Geometry Unit 12, Day 9 http://jwelker.lps.org/lessons/ppt/geod_3_3_slope.ppt

2. Slope - Defined Given two points (x 1, y 1 ) and (x 2, y 2 ), the slope m of a line is defined to be:

3. Slope – Example #1 Given two points A(-3, -4) and B(3, 5), find the slope of the line through the points. Solution: Reduce fractions whenever possible.

4. Slope – Example #2a Find the slope of the line AB. A(-4, 4) B(1, 7) The slope of the line through AB is 3/5.

5. Slope – Example #2c On your own: Find the slope of EF. The slope of EF is -2/3. Since the slope is negative, the line runs down as we look from left to right. Positive slope runs up from left to right.

6. Slope – Example #2d On your own: Find the slope of CF. C(3,7) F(3, -6) Since division by zero is not defined, the slope of CF is undefined.

7. Slope – Vertical Lines The slope of any vertical line is undefined.

8. Slope – Example #3 On your own: Find the slope of MN. M(-1, 2) N(3, 2) The slope of MN is 0. MN is said to have zero slope.

9. Slope – Horizontal Lines The slope of any horizontal line is zero.

10. Slope – Other Lines Find the slope of PQ, RS, and TU. What can be said about lines PQ and RS? The lines are parallel and have the same slope.

11. Slope – Parallel Lines Parallel lines have equal slopes.

12. Slope – Other Lines What can be said about lines PQ and TU? The lines are perpendicular and have slopes which multiply to -1.

13. Slope – Perpendicular Lines Perpendicular lines have slopes which: multiply to -1 are negative reciprocals of each other. Horizontal and vertical lines are perpendicular to each other.

14. Slope – Example #4 Points R(3, -2) and S(-1, 3) form a line. a)find the slope of RS. b)find the slope of a line perpendicular to RS. Since perpendicular lines have slopes which are negative reciprocals, the slope of the perpendicular line is 4/5.

15. Practice Matching Game: Calculate the slope!  http://www.quia.com/mc/499415.html http://www.quia.com/mc/499415.html

16. Homework Work Packet: Slope, Parallel and Perpendicular Lines