Unit 7, Lesson 2
Adjacent Angles
Grade 7
Preparation
Lesson Narrative
In this lesson, students are introduced to the terms complementary and supplementary for describing specific angle relationships. They practice finding an unknown angle given the measure of another angle that is complementary or supplementary.
Students use repeated reasoning with many pairs of angles to conclude that a pair of complementary angles will have measures that add up to 90 degrees, and a pair of supplementary angles will have measures that add up to 180 degrees (MP8).
- Comprehend the terms “complementary” and “supplementary” (in spoken and written language) as they pertain to pairs of angles.
- Explain (orally and in writing) how to find an unknown angle measure, given adjacent complementary or supplementary angles.
- Generalize (orally) that when a straight angle or a right angle is decomposed, the measures of the resulting angles add up to $180^\circ$ or $90^\circ$, respectively.
Let’s look at some special pairs of angles.
Required Materials
Activity 2
Required Preparation
None
Complementary angles have measures that add up to 90.
For example, a angle and a angle are complementary.