Instructional Activity# Triangle ONE Plus

Lesson 10. Unit 1. Grade 8 Open Up Resources

Open Up Resources10 min(s)

This Instructional Activity is a part of the Lesson 10, Unit 1, Grade 8. This activity builds upon the ideas of the previous one. This time a pattern is built from a single triangle via reflections and the goal is to study the angles and side lengths in this pattern as it grows. If they build the pattern carefully, students may notice after putting together 6 triangles, like in the previous activity, that two of the sides of the triangles (one side of the original and one side of the 6th) lie on the same line. The 6 triangle pattern can be reflected over this line to make it "complete" with 12 copies of the original triangle. Alternatively, students may notice the right angle made by 3 triangles and reason that they can complete a circle with 4 right angles.