In this lesson, the student is introduced to the idea of complementary and supplementary angles. A mnemonic is used to help the student remember that if a straight line exists, the angles will be supplementary.
In this lesson, the student learns about vertical angles. The student first learns some other potential names for vertical angles, like opposite angles, and then the student is shown that vertical angles are equal. Then, the lesson shows that the other two angles can be shown using the properties of supplementary angles.