90° — Right Angle 0° - 90° — Acute angle 90° - 180° — Obtuse angle. 180° - 360° — Reflex angle.
Angles are also sometimes expressed in radians, with 2 * Pi radians representing an entire revolution. A radian is therefore just over 57 degrees. Pi itself is defined as the ratio of the circumference to the diameter for a circle. See also the separate entry for 'Pi'. |