Coterminal angles are angles that share the same terminal side. They differ by multiples of 360° (or 2π radians):
\[ \theta_{\text{coterminal}} = \theta + 360° \times k \quad \text{or} \quad \theta_{\text{coterminal}} = \theta + 2\pi k \]where \(k\) is any integer. This calculator finds the principal coterminal angle in [0°, 360°) or [0, 2π).
Quadrant I: 0 to π/2 | Quadrant II: π/2 to π
Quadrant III: π to 3π/2 | Quadrant IV: 3π/2 to 2π
Axes: 0, π/2, π, 3π/2, 2π