Identifying Perpendicular Lines in Geometric Shapes

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: What is Symmetry in Math? - Definition & Concept

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:05 Perpendicular Lines
  • 0:31 Squares & Rectangles
  • 1:44 Triangles & Trapezoids
  • 3:02 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed Audio mode

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Do you know what a perpendicular line is? Do you know how to spot one in a geometric shape? This lesson will tell you how to spot perpendicular lines in squares, rectangles, triangles, and trapezoids.

Perpendicular Lines

Lines on a paper, lines on a road, lines of people in front of a store - lines are used and seen everywhere, including in the world of math!

Let's angle this line-based lesson the right way from the very start! We'll be taking a look at how to identify special types of lines here. They are called perpendicular lines.

Perpendicular lines are lines that are found at right angles to one another. A right angle is exactly 90 degrees.

Squares & Rectangles

Right then. Right angles can be found in all sorts of geometric shapes. Let's start with the square.

square right angle symbol

Actually, the square on the screen right now is the proper symbol for a right angle. So if you ever see it drawn next to a pair of lines like you see now, you'll know that those lines are at a right angle to one another, even if your protractor says otherwise! This means, by definition, those two lines are also perpendicular to one another!

square with four right angles

Let's look at the square. The square is made of four lines. Because each line is perpendicular to two other lines, a square has four right angles.

Line AB is perpendicular to BC. BC is perpendicular to CD as well as AB and so forth.

So, yes, to make things clear: a square has right angles, and a square drawn by two additional lines in the corner of a right angle is used to symbolize a right angle as well.

rectangle with four right angles

Rectangles also have right angles. Again, let's look at the rectangle on our screen. Like a square, a rectangle has lines that are perpendicular to two other lines. This means it also has four right angles.

Triangles & Trapezoids

When it comes to triangles, things aren't as easy. That's because rectangles and squares must have four right angles, but a triangle may not have any!

So how do we know if a triangle has a right angle, and therefore, has perpendicular lines?

Well, if you have a square next to two lines in a triangle or someone tells you the triangle is a right triangle, then you know two of its lines must be perpendicular to one another and they form a right angle.

right triangle perpendicular

The image you see now has a little square in the corner, and that tells us this is a right angle, a right triangle, and thus, lines AC and CB are perpendicular to one another.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account