Slopes of Perpendicular Lines

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?