Math Homework. Do It Faster, Learn It Better.

Reference Angle

Let θ  be a non-quadrantal angle in standard position.   Its reference angle is the acute angle α formed by the terminal side of θ and the horizontal axis.


Quadrant I :

  The given angle and the reference angle are the same angle.




Quadrant II :

                               α=πθ (radians)

                               α=180°θ (degrees)



Quadrant III :

                               α=θπ (radians)

                                α=θ180° (degrees)



Quadrant IV :

                                  α=2πθ (radians)

                                  α=360°θ (degrees)