\[\sin^{2} A + \cos^{2} A = 1\]
\[\sec^{2} A – \tan^{2} A = 1\]
\[\csc^{2} A – \cot^{2} A = 1\]
\[\tan A \cdot \cot A = 1\]
\[\sin A \cdot \cos A = 1\]
\[\cos A \cdot \sec A = 1\]