Table of Contents Unit Circle Sum-Difference Identities Cosine Sine Tangent Double Angle Identities Sine Cosine Tangent Product Identities Cosine-Cosine Sine-Sine Sine-Cosine Cosine-Sine T-Formulae Inverse Trigonometric Functions Notation $y=\sin^{-1}(x)$ $y=\cos^{-1}(x)$ $y=\tan^{-1}(x)$ Properties That’s all of Extension 1 Trigonometry (for year 11, anyway).