This Instructional Activity is a part of the Lesson 10, Unit 1, Grade 8. This activity continues the previous one, building a more complex shape this time by adding an additional copy of the original triangle. The three triangle picture in the task statement will be important later in this unit when students show that the sum of the three angles in a triangle is 180 degree. To this end, encourage students to notice that the points E, A, and D all lie on a line. As with many of the lessons applying transformations to build shapes, students are constantly using their structural properties to make conclusions about their shapes. Specifically, that rigid transformations preserve angles and side lengths.