Does the law of cosines:
$c^2 = a^2 + b^2 - 2 a b \cos \theta$
work with imaginary angles? to get something like:
$c^2 = a^2 + b^2 - 2 a b \cosh \theta$
Alternatively, is there a hyperbolic equivalent for the law of cosines that has a similar form to the law of cosines? I know there's a hyperbolic law of cosines that involves cosh's and sinh's but I want something that looks like the regular law of cosines.