sinh, cosh, tanh, asinh, acosh, atanh - hyperbolic functions
These functions compute the designated direct and inverse hyperbolic
functions for real arguments. They inherit much of their roundoff
error from expm1() and log1p, described in exp(3M).
These functions handle exceptional arguments in the spirit of ANSI/IEEE
Std 754-1985. Thus sinh() and cosh() return +- on overflow, acosh()
returns a NaN if its argument is less than 1, and atanh() returns a NaN
if its argument has absolute value greater than 1. In addition,
sinh,cosh, and tanh() may also set errno and call matherr(3M).
22 november 1987 HYPERBOLIC(3M)