Prosthaphaeresis Formulas/Hyperbolic Sine plus Hyperbolic Sine

Theorem

 * $\sinh x + \sinh y = 2 \sinh \left({\dfrac {x + y} 2}\right) \cosh \left({\dfrac {x - y} 2}\right)$

where $\sinh$ denotes hyperbolic sine and $\cos$ denotes hyperbolic cosine.