#include <math.h>
float coshf(float x);
coshf calculates the hyperbolic sine of x.
If |x| >~ 88.7228, errno is set to EDOM and coshf returns HUGE_VALF.
If x is +?, -?, or NaN, coshf returns |x|.
If |x| >~ 88.7228, coshf returns +? or
-? depending upon the sign of x.
coshf conforms to ISO/IEC 9899:1990 (C90) and ISO/IEC 9899:1999 (C99).