# Slopes of Perpendicular Lines

- Author:
- Marina Kostuch

## Perpendicular Lines

Two lines are perpendicular when they intersect at 90 degree angles.
Two lines are graphed in the plane. The slope of the first line is a/b. The slope of the second line is c/d.

## Slopes of Perpendicular Lines

## Set a = 2 and b = 3.

This means the slope of the purple line is 2/3. Change "c" and "d" until the angle formed between the two lines is a right angle. What are the values of "c" and "d"?

## Set a = -4 and b = 1

This means the slope of the purple line is -4. Change "c" and "d" until the angle formed between the two lines is a right angle. What are the values of "c" and "d"?

## Product of Slopes

What is the product of the slopes of two perpendicular lines?

## Slopes of Perpendicular Lines

By examining the equations, how do you know when two lines will be perpendicular when graphed?