Angles (arguments of functions): \(\alpha\), \(\beta\)

Trigonometric functions: \(\sin \alpha,\) \(\cos \alpha,\) \(\tan \alpha,\) \(\cot \alpha\)

- Product of sines

\(\sin \alpha \cdot \sin \beta =\) \( \large\frac{{\cos \left( {\alpha – \beta } \right) – \cos \left( {\alpha + \beta } \right)}}{2}\normalsize\) - Product of cosines

\(\cos \alpha \cdot \cos \beta =\) \( \large\frac{{\cos \left( {\alpha – \beta } \right) + \cos \left( {\alpha + \beta } \right)}}{2}\normalsize\) - Product of sine and cosine

\(\sin \alpha \cdot \cos \beta =\) \( \large\frac{{\sin \left( {\alpha – \beta } \right) + \sin \left( {\alpha + \beta } \right)}}{2}\normalsize\) - Product of tangents

\(\tan\alpha \cdot \tan \beta =\) \( \large\frac{{\tan\alpha + \tan \beta }}{{\cot\alpha + \cot \beta }}\normalsize\) - Product of cotangents

\(\cot\alpha \cdot \cot \beta =\) \( \large\frac{{\cot\alpha + \cot \beta }}{{\tan\alpha + \tan \beta }}\normalsize\) - Product of tangent and cotangent

\(\tan\alpha \cdot \cot \beta =\) \( \large\frac{{\tan\alpha + \cot \beta }}{{\cot\alpha + \tan \beta }}\normalsize\)