acosh - inverse hyperbolic cosine function


SYNOPSIS

       #include <math.h>

       double acosh(double x);


DESCRIPTION

       The  acosh()  function  calculates  the inverse hyperbolic
       cosine of x; that is the value whose hyperbolic cosine  is
       x.   If  x  is less than 1.0, acosh() returns not-a-number
       (NaN) and errno is set.


ERRORS

       EDOM   x is out of range.


CONFORMING TO

       SVID 3, POSIX, BSD 4.3, ISO 9899


SEE ALSO

       asinh(3), atanh(3), cosh(3), sinh(3), tanh(3)