double
     atanh(double x);

     long double
     atanhl(long double x);

     float
     atanhf(float x);

DESCRIPTION

     The atanh() function computes the inverse hyperbolic tangent of the real
     argument x.

SPECIAL VALUES

     atanh(+-0) returns +-0.

     atanh(+-1) returns +-infinity and raises the "divide-by-zero" floating-
     point exception.

     atanh(x) returns a NaN and raises the "invalid" floating-point exception
     for |x| > 1.

SEE ALSO

     acosh(3), asinh(3), exp(3), math(3)

STANDARDS

     The atanh() function conforms to ISO/IEC 9899:1999(E).

4.3 Berkeley Distribution      November 20, 2002     4.3 Berkeley Distribution