Manpages - atanh.3

atanh, atanhf, atanhl - inverse hyperbolic tangent function

  #include <math.h>

  double atanh(double x);
  float atanhf(float x);
  long double atanhl(long double x);

Link with -lm.

Feature Test Macro Requirements for glibc (see *feature_test_macros*(7)):

*atanh*():

      _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
          || _XOPEN_SOURCE >= 500
          || /* Since glibc 2.19: */ _DEFAULT_SOURCE
          || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

*atanhf*(), *atanhl*():

      _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
          || /* Since glibc 2.19: */ _DEFAULT_SOURCE
          || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

These functions calculate the inverse hyperbolic tangent of x; that is the value whose hyperbolic tangent is x.

On success, these functions return the inverse hyperbolic tangent of x.

If x is a NaN, a NaN is returned.

If x is +0 (-0), +0 (-0) is returned.

If x is +1 or -1, a pole error occurs, and the functions return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with the mathematically correct sign.

If the absolute value of x is greater than 1, a domain error occurs, and a NaN is returned.

See *math_error*(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

Domain error: x less than -1 or greater than +1

errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised.

Pole error: x is +1 or -1

errno is set to ERANGE (but see BUGS). A divide-by-zero floating-point exception (FE_DIVBYZERO) is raised.

For an explanation of the terms used in this section, see *attributes*(7).

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning double also conforms to SVr4, 4.3BSD.

In glibc 2.9 and earlier, when a pole error occurs, errno is set to EDOM instead of the POSIX-mandated ERANGE. Since version 2.10, glibc does the right thing.

*acosh*(3), *asinh*(3), *catanh*(3), *cosh*(3), *sinh*(3), *tanh*(3)

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