How to Construct a Triangle When Given the Angles

By Marija Kero

Constructing a triangle when given the three angles will require you to pay close attention to the lengths. Construct a triangle when given the three angles with help from an experienced mathematics professional in this free video clip.


Hi, my name is Marija, and today I'm gonna show you how to construct the triangle when given three angles. So if you're not given any lengths, then you're gonna have to makeup a length and let the triangle form itself. So we're gonna start with one segment, AB, and you're gonna have to choose the length, so let's say that you make it 5 inches long. You're gonna create an angle from A, and another angle from B, and you'll let the third angle create itself. So let's say that you know the three measurements of the triangle are 50 degrees, 60 degrees and 70 degrees. What you'll do is using A as the vertex of your angle, you'll create a 50 degree angle with your protractor. So, it will be exact when you have your protractor, but you'll draw an angle that is 50 degrees. And then you'll come to point B, and using point B as the vertex of another angle and your protractor, you'll create an angle that is 60 degrees. So approximately like this. Now what you'll do is you're gonna keep drawing, keep extending your raise here until they connect, and when they do, they will naturally have to form an angle that is 70 degrees. So when you're not given the specific length, you can pick on yourself, draw an angle from the vertex on the left, draw an angle from the vertex of the right, and then extend them until they make your third angle, which will have to be 180 minus the other two degrees. That is how you draw a triangle when given three angles.

About the Author

Marija Kero graduated from the Pforzheimer Honors College at Pace University with a Bachelor's Degree in Mathematics and Adolescent Education.