Complementary Angles

Two angles are complementary angles when the sum of their measures is 90^(∘).

In the diagram, ∠ B and ∠ E are complementary because the sum of their measures is equal to 90^(∘). m ∠ B + m ∠ E = 90 ^(∘) When using radians as the unit of measure, two angles are complementary when the sum of their measures is π2, or about 1.57, radians. m ∠ B + m ∠ E = π/2 Notice that if two angles are complementary, they are by necessity acute angles. Also, if two complementary angles are adjacent, the angle formed by the not common sides is a right angle.