There are several types of triangles in geometry, each with different side lengths and angles in relation to one another, but all triangles have one characteristic in common: They all have three angles that add to 180 degrees. This characteristic allows you to take unknown measurements from a triangle and subtract them from 180 to determine any remaining angles. You can also measure the angles with a protractor and compare.

Align the horizontal edge of the protractor with the base of the triangle.

Place the center point of the protractor on the vertex of the angle.

## Sciencing Video Vault

Follow the side of the triangle until it reaches the angle measurement mark. Note the measurement.

Repeat for any other angles you want to find.