Learning goals: Teacher Facing Comprehend the phrase “similar polygons” (in written and spoken language) to mean the polygons have congruent corresponding angles and proportional side lengths. Critique (orally) arguments that claim two polygons are similar. Justify (orally) the similarity of two polygons given their angle measures and side lengths. Full lesson plan (warm-up, activities, synthesis, cool-down prompt) from 8.2 Dilations, Similarity, and Introducing Slope, Grade 8.