Coterminal angles

Math

Definition

Coterminal angles are angles that share the same terminal side when drawn in standard position. You find coterminal angles by adding or subtracting full rotations (360° or 2π radians).

Examples

  • 30° and 390° are coterminal because 390° - 360° = 30°
  • −45° is coterminal with 315°
  • π/3 and 7π/3 are coterminal because 7π/3 - 2π = π/3
Key Fact

Coterminal angles: θ ± 360°n (degrees) or θ ± 2πn (radians)

Related Terms

Reference angles Degree to radian conversion Measuring angles Unit circle

Study This Concept

Practice coterminal angles with free review games in these units:

Trigonometry Unit 1: Angles and Radian Measure