# Forum Thread: How to Determine if a Line Is Perpendicular.

What are perpendicular lines or what is perpendicular? Well perpendicular are two lines that intersect at 90 degree angles. So let's look at a couple of examples of where we will see those. So we have two lines and they are intersecting at 90 degree angles, and I will label it with a little box that represents 90 degrees, and once we know this is 90 degrees we know the other three are 90 degrees because these are lines and lines have a degree of 180 so that would make all four of these 90 degrees. Now let's look at the two line segments. This angle is 90 degrees and you will often see this in a right triangle. So a right triangle has two segments that are perpendicular and measure 90 degrees. So that is perpendicular lines. Hope this helps

## What is a perpendicular line What is a perpendicular line? A perpendicular line is one that intersects another line at a right angle.Includes video and perpendicular calculator

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