This Instructional Activity is a part of the Lesson 11, Unit 2, Grade 8. Ask students if they really need to do all of the work they did in part of Exercise 1. Students should say no. The reason they do not need to do all of that work is because they already know that translations, rotations, and reflections preserve angle measures and lengths of segments. Ask students to help summarize the basic properties of all three basic rigid motions.