Open Up Resources 40 min(s)

In this lesson, students justify that alternate interior angles are congruent, and use this and the vertical angle theorem, previously justified, to solve problems. Show that alternate interior angles are congruent. Introduce the standard transversal diagram, with two parallel lines cut by one transversal. Learning targets: If students have two parallel lines cut by a transversal, students can identify alternate interior angles and use that to find missing angle measurements.