# 8.G.A.5

Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles. For example, arrange three copies of the same triangle so that the sum of the three angles appears to form a line, and give an argument in terms of transversals why this is so.

## Tasks

Find the Missing Angle

Find the Angle

Tile Patterns I: octagons and squares

Tile Patterns II: hexagons

Rigid motions and congruent angles

A Triangle's Interior Angles

Congruence of Alternate Interior Angles via Rotations

Street Intersections

Similar Triangles II

Similar Triangles I