21: A ngle Relationships in Parallel Lines and Triangles

21.1 Parallel Lines Cut by Transversal

 Magic of Math Parallel Lines Cut by Transversal

Video on this lesson here   and here

Geogebra play with transversals HERE

Practice this lesson here

practice finding equations and solving here  and here

21.3  Angle Similarity

21.2  Angle Theorems for Triangles  Interior & Exterior

Viedo on Proof of why sum of triangles is 180 degrees HERE

Video on exterior angles using the remote interior angles HERE

practice on exterior angles here