ACOSH(3)

NAME
       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)