CC 8G-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.

Grade: 8

Domain: Geometry

Cluster: Understand congruence and similarity using physical models, transparencies, or geometry software.

All Standards Common Core Standards K-8