In this video lesson, students see that angles do not need to be adjacent to be complementary or supplementary. Students are also introduced to and begin to use the term vertical angles for describing the opposite angles formed when two lines cross (MP6). They examine multiple examples and see that the vertical angles have equal measures. Students can relate this understanding to the fact that both angles in a pair of vertical angles are supplementary to the same angle in between. As students see different ways of making pairs of supplementary angles in two crossing lines, they engage in MP7.

Grade 7, Episode 23: Unit 7, Lesson 3 | Illustrative Math