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Angles of a Triangle

Angles of a Triangle

Author: Seth Marx

To understand that the angles of a triangle always add up to 180 degrees, as well as know what exterior angles are and how to find them.

This packet gives a basic overview of the interior and exterior angles of a triangle.

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New Terms

Interior Angles of a Triangle: the angles on the inside of a triangle; always add up to 180 degrees

Exterior Angles of a Triangle: the angle between one side of a triangle and an extension of the adjacent side


This video gives a visual of how the interior angles of a triangle relate to one another (by adding up to 180 degrees), and gives a few examples with variables toward the end.

Exterior Angle Theorem

This video explains exterior angles and their relationship to the interior angles of a triangle (also called the exterior angle theorem).