ATANH(3)

NAME
       atanh - inverse hyperbolic tangent function

SYNOPSIS
       #include <<math.h>>

       double atanh(double x);

DESCRIPTION
       The  atanh()  function  calculates  the inverse hyperbolic
       tangent of x; that is the value whose  hyperbolic  tangent
       is  x.   If  the  absolute value of x is greater 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) acosh(3) cosh(3) sinh(3) tanh(3)