Instructional Activity# Triangle Plus One

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. The purpose of this task is to use rigid transformations to describe an important picture that students have seen in grade 6 when they developed the formula for the area of a triangle. The language "compose" is a grade 6 appropriate way of talking about a 180 degree rotation. The focus of this activity is on developing this precise language to describe a familiar geometric situation. Students need to remember and use an important property of 180 degree rotations, namely that the image of a line after a 180 degree rotation is parallel to that line.