1. 3.7 Perpendicular Lines in the Coordinate Plane

2. Postulate 18 “Slopes of Perpendicular Lines” In a coordinate plane, 2 non-vertical lines are perpendicular if and only if the product of their slopes is -1. Vertical and Horizontal Lines are Perpendicular.

3. Example 1: Deciding whether the lines are perpendicular. Line h:The slope of h is 3/4. Line j:The slope of j is -4/3. So the lines are perpendicular.

4. Example 2: Deciding whether the lines are perpendicular. Line a:The slope of a is -2/3. Line b:The slope of b is -3/2. So the lines are NOT perpendicular. The Product needs to be -1.

5. Example 3: Deciding whether the lines are perpendicular. Line r:Line s: The product of the slopes is 1, not -1. So, r and s are not perpendicular.

6. Example 4: Find an equation of a perpendicular line. Line t has an equation. Find an equation of the line s that passes through P(4,0) and is perpendicular to t.