Unit 1, Lesson 16# Parallel Lines and the Angles in a Triangle

Open Up Resources 45 min(s)

Parallel Lines and the Angles in a Triangle Use rigid transformations to informally establish the Triangle Sum Theorem, that the sum of the angle measures in a triangle. Let's see why the angles in a triangle add to 180 degrees. Learning targets: students can explain using pictures why the sum of the angles in any triangle is 180 degrees.