# Angles Inside and Outside of Triangles Math Games

In this series of games, your students will learn that to use informal arguments to establish facts about the angle sum and exterior angle of triangles. The Similarity Through Transformations learning objective — based on CCSS and state standards — delivers improved student engagement and academic performance in your classroom, as demonstrated by research. This learning objective directly references 8.G.A.5 as written in the common core national math standards.

Scroll down for a preview of this learning objective’s games and the concepts.

**Concepts Covered**

Two parallel lines cut by a transversal create a series of angles that have a relationship. Corresponding angles are congruent (same side of the transversal and same relative place on the parallel lines; above the parallel lines and to the left of the transversal). Vertical angles are congruent (share a vertex and a side). Alternate interior angles are congruent (every other angle inside the parallel lines). Alternate exterior angles are congruent (every other angle outside the parallel lines). Non-congruent special angles are supplementary.

Given two (interior) angles in a triangle, their sum must be less than 180 degrees. If the sum were equal to 180, then the triangle would have two parallel sides, and thus no third vertex. Given a triangle, cut the three angles and place side by side to show that all three angles when adjacent form a 180 angle or a straight line.

Identify angle relationships with parallel lines and use to solve for unknown angles. Identify angle relationships with parallel lines and provide a mathematical statement regarding angle measurements. Identify angle relationships in a diagram without parallel lines and use to determine the unknown angle. Determine angle measures using triangles.

A preview of each game in the learning objective is found below.

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