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)