Build student understanding of the Triangle Sum Theorem with guided notes and video support! This resource helps students see why the interior angles of a triangle always add up to 180° through clear examples, scaffolded notes, and practice problems. What’s Included: Student notes/worksheet introducing the Triangle Sum Theorem Companion instructional videos in English, Spanish, and French Video walk-through of the first 3 problems, with students completing #4 and #5 independently for practice