Perpendicular Lines

Perpendicular lines are two lines that meet at a right angle. A right angle is a square corner, like the corner of a book. When lines cross this way, they form four equal corners. Perpendicular lines are an important idea in math. You can find them in shapes and buildings everywhere.

Right Angles

A right angle looks like the letter L. It measures exactly 90 degrees. When two lines meet at this angle, they are perpendicular. You can check with a corner of a piece of paper. If the corner fits perfectly where the lines meet, they are perpendicular.

Where to Find Them

Perpendicular lines are everywhere you look. The walls of a room meet the floor at perpendicular angles. The hands of a clock are perpendicular at 3:00 and 9:00. The letter T and the letter L both have perpendicular lines. Builders use perpendicular lines to make sure walls stand up straight.

Fun Facts

• The small square symbol shows that an angle is a right angle.
• Perpendicular means 'hanging straight down' in Latin.
• A flagpole is usually perpendicular to the ground.

Did You Know?

Builders use a special tool called a square to check if lines are perpendicular when they are constructing a house.