Description: Define the hyperbolic sine function (sinh). We define it this way for
cmpt , which requires the form ( x e. A |-> B ) . See
sinhval-named for a simple way to evaluate it. We define this function
by dividing by _i , which uses fewer operations than many conventional
definitions (and thus is more convenient to use in set.mm). See
sinh-conventional for a justification that our definition is the same as
the conventional definition of sinh used in other sources. (Contributed by David A. Wheeler, 20-Apr-2015)