Lesson 2-3 Part 1: Triangle Angle Sum Proof

How can we use our understanding of angles 1 through 5 to prove that every triangle must have 180 degrees?
How can we use what we know about angles 1 through 5 to prove that a triangle must have 180 degrees?
– GENOVEVA ABREU SANCHEZ, Shaun Errichiello

Information: Lesson 2-3 Part 1: Triangle Angle Sum Proof