addition formula (original) (raw)

The five first of those are instances of ; e.g. cosh⁡x and sinh⁡x are tied together by the algebraic connection (http://planetmath.org/UnitHyperbola) cosh2⁡x-sinh2⁡x=1.

One may also speak of the subtraction formulae of functions — one example would be ex-y=exey.