Vocabulary
adjacent angles, complementary angles
TEKS 7(1)(E), 7(11)(C)
Two angles are complementary angles if the sum of their measures is 90°.
Complementary angles that are adjacent form a right angle. ∠ AOB and ∠ BOC are complementary adjacent angles.
As the measures of the two angles change, the sum of their measures is still 90°.
Suppose two complementary angles are not adjacent. Even though ∠ AOB and angle ∠ BOC are not adjacent, the sum of their measures remains 90° as the measures of the two angles change.
TEKS 7(1)(E), 7(11)(C)
Example Finding Complements of Angles
Draw an adjacent complement for each angle. What is the measure of each complement?
a.
b.
c.
Solution
a.
The measure of the complement is 90° − 80°, or 10°.