# How to Construct a Perpendicular Line Through a Point

By Rachel KaploveConstructing a perpendicular line through a point is something that will require you to pay close attention to the angle. Construct a perpendicular line through a point with help from a professional private tutor in this free video clip.

### Transcript

Hi, I'm Rachel, and today we're going to be going over how to construct a perpendicular line through a point. So, let's say we have a point like this, and it's gonna need to be on a line in order to find something that's perpendicular to it. So, in order to find something that's perpendicular, we want to find something that forms a 90 degree angle, like this. So, if we go straight 90 degrees, we form a perpendicular line from that point. Now if you're talking about doing this on a graph, you want to find a line that is the negative reciprocal. What does that mean, of the slope? So, this means that if one line has a slope of y equals 3x plus four, a line that's going to be perpendicular to that point is going to have the negative reciprocal, so y equals negative one-third x, and anything on that line will be perpendicular to this point. I'm Rachel, and thank you for learning with me today.