Deciding on symbols: An angle $\theta$ Smallest non-negative coterminal $0\leq\theta^{\equiv}< 2\pi$ Reference angle (rotation from x-axis) $0\leq\theta^\sim \leq \frac{\pi}2$ Complement $(90\degree-\theta\degree)=\theta^{\large{\llcorner}}\degree \text{ or } (\frac{\pi}2 - \theta) = \theta^{\large{\llcorner}}$ Supplement $(180\degree-\theta\degree)=\theta^\perp\degree \text{ or } (\pi - \theta) = \theta^{\large{\lrcorner\llcorner}}$ [[Coterminal angles]] [[Reference Angle]] [[Definition of the Circular Trigonometric Functions]] [[Pythagorean Identities]] [[Angle Sum-or-Difference Identities]] [[Double-or-Half Angle Identities]] [[Power Reduction Identities]] [[Exact values for trig functions]]