http://www.ck12.org Chapter 3. Parallel and Perpendicular Lines
3.9 Perpendicular Lines in the Coordinate Plane
Here you’ll learn properties of perpendicular lines in the coordinate plane, and how slope can help you to determine
whether or not two lines are perpendicular.
What if you wanted to figure out if two lines in a shape met at right angles? How could you do this? After completing
this Concept, you’ll be able to use slope to help you determine whether or not lines are perpendicular.
Watch This
MEDIA
Click image to the left for more content.CK-12 Foundation: Chapter3PerpendicularLinesintheCoordinatePlaneA
Watch the portion of this video that deals with Perpendicular Lines
MEDIA
Click image to the left for more content.KhanAcademy: Equations of Parallel and Perpendicular Lines
Guidance
Recall that the definition ofperpendicularis two lines that intersect at a 90◦, or right, angle. In the coordinate plane,
that would look like this:
If we take a closer look at these two lines, we see that the slope of one is -4 and the other is^14. This can be generalized
to any pair of perpendicular lines in the coordinate plane.The slopes of perpendicular lines are opposite signs
and reciprocals of each other.
Example A
Find the slope of the perpendicular lines to the lines below.
a)y= 2 x+ 3
b)y=−^23 x− 5
c)y=x+ 2
We are only concerned with the slope for each of these.