Simpson's Formulas/Cosine by Cosine

Theorem

 * $\cos \alpha \cos \beta = \dfrac {\map \cos {\alpha - \beta} + \map \cos {\alpha + \beta} } 2$

where $\cos$ denotes cosine.

Also see

 * Simpson's Formula for Sine by Sine
 * Simpson's Formula for Sine by Cosine
 * Simpson's Formula for Cosine by Sine