3.7 perpendicular lines in the coordinate plane
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3.7 Perpendicular Lines in the Coordinate Plane. 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. - PowerPoint PPT PresentationTRANSCRIPT
3.7 Perpendicular Lines in the Coordinate Plane
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.
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.
3 24
y x
4 33
y x
3 4 12 14 3 12
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.
2 13
y x
3 12
y x
2 3 6 13 2 6
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.
4 5 2
5 4 24 25 5
45
x y
y x
y x
Slope
5 4 3
4 5 35 34 4
54
x y
y x
y x
Slope
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.
2 1y x
12
12102
Perpendicular Slope
y mx b
y x b