Unit 2, Lesson 14# More on the Angles of a Triangle

EngageNY 45 min(s)

Students know a third informal proof of the angle sum theorem. Students know how to find missing interior and exterior angle measures of triangles and present informal arguments to prove their answer is correct. Students see one final informal proof of the angle sum of a triangle before moving on to working with exterior angles of triangles. Let's look at one final proof that the sum of the degrees of the interior angles of a triangle is 180°.