Topic summary
Acute Angle
Extracted from the Wikipedia article Angle.
Combining angle pairs
Complementary angles are angle pairs whose measures sum to a right angle (1/4 turn, 90°, or π/2 rad). If the two complementary angles are adjacent, their non-shared sides form a right angle. In a right-angle triangle the two acute angles are complementary as the sum of the internal angles of a triangle is 180°. The difference between an angle and a right angle is termed the complement of the angle.