Grade 8 · Geometry

CCSS.MATH.CONTENT.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.

Read this standard on the official Common Core site

Lessons that teach this standard

• Angles in Triangles: The Angle Sum and Exterior Angles

  Why the angles of a triangle add to 180 degrees, what the exterior angle theorem says, and how parallel lines cut by a transversal produce equal angles.