21: A ngle Relationships in Parallel Lines and Triangles

21.1 Parallel Lines Cut by Transversal

               Notes here

Video on this lesson here   and here

Geogebra play with transversals HERE

Practice this lesson here

practice finding equations and solving here  and here

21.2   Equations with angles

21.3  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