Werner Formulas

$\begin{displaymath} 2\sin\alpha\cos\beta=\sin(\alpha-\beta)+\sin(\alpha+\beta) \end{displaymath}$

(1)

$\begin{displaymath} 2\cos\alpha\cos\beta=\cos(\alpha-\beta)+\cos(\alpha+\beta) \end{displaymath}$

(2)

$\begin{displaymath} 2\cos\alpha\sin\beta=\sin(\alpha+\beta)-\sin(\alpha-\beta) \end{displaymath}$

(3)

$\begin{displaymath} 2\sin\alpha\sin\beta=\cos(\alpha-\beta)-\cos(\alpha+\beta). \end{displaymath}$

(4)

See also Trigonometry