Triangles and Angles

In this lesson, you'll learn how to use your knowledge of angle measures in a triangle to solve for unknown angles. The key idea is that within a triangle, if you add all the angles, it will add up to 180 degrees, the same as a straight line. You can use this idea to solve problems involving exterior angles and opposite interior angles. By the end of the lesson, you'll be able to apply these concepts to solve any problem in section 4-2.

Learn how to use your knowledge of angle measures in a triangle to solve for unknown angles.

• How do you find unknown angle measures in a triangle?
• If two angles in a triangle are 87 and 58 degrees, what is the third angle measure?
• If two angles form a straight line and one angle is 35 degrees, what is the other angle?
• What is an exterior angle, and how do you find its measure?
• What are vertical angles?