1. Perpendicular Lines in the Coordinate Plane
Section 3.7

2. Negative Reciprocals
Negative reciprocals are numbers whose product is -1.
Examples:

3. Slopes of Perpendicular Lines
In a coordinate plane, two nonvertical lines are perpendicular if and only if their slopes are negative reciprocals.
Think: product of -1.

4. Examples!!
The slopes of two lines are given. Are the lines perpendicular? 1.
YES!! 2.
NO WAY!!!

5. More Examples!
Lines a and b are perpendicular. The slope of line a is given. What is the slope of line b? 3. 4.

6. Find the slope of the two lines
Find the slope of the two lines. Decide if the two lines are perpendicular.
YES!!

7. Assignment
p.175: 7-24

8. More with Perpendicular Lines in the Plane
(Still) Section 3.7

9. Recall from yesterday…
…lines that are perpendicular have
slopes that are
negative reciprocals.
(Hint: Their product is -1…)

10. Decide whether the lines are perpendicular.
YES!!!

11. Decide whether the lines are perpendicular.
NO!!
To find the slopes, write in slope-intercept form!

12. Find the slope of each line
Find the slope of each line. Identify any parallel and perpendicular lines.
Find the slope of each line. Identify any parallel or perpendicular lines.

13. Assignment p.176: 25-36 QUIZ TOMORROW! Sec. 3.4-3.7
Be sure you know how to prove two lines parallel
There will be one proof (your choice: two-column or flow proof)