3-4: Supplementary Angles

Key Concept

Two angles are supplementary angles if the sum of their measures is 180°. Supplementary angles that are adjacent form a straight angle. ∠ AOB and ∠ BOC are supplementary adjacent angles.

Adjacent angles AOB and BOC each measure 90°.

Notice that as the measures of the two angles change, the sum of their measures is still 180°.

Suppose two supplementary angles are not adjacent.

Even though ∠ AOB and ∠ BOC are not adjacent, the sum of their measures remains 180° as the measures of the two angles change.

Angle AOB measures 160°. Angle BOC measures 20°.


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Table of Contents

Digits, Grade 7, Volume 1, Homework Helper Unit A: Number and Operations Unit B: Expressions, Equations, and Relationships Unit C: Measurement and Geometry Unit D: Proportionality English/Spanish Glossary Formulas Math Symbols Formulas Measures Properties