atanh, atanhf, atanhl - inverse hyperbolic tangent function
#include <math.h> double atanh(double x); float atanhf(float x); long double atanhl(long double x);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 500 || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
These functions calculate the inverse hyperbolic tangent of
x; that is the value whose hyperbolic tangent is
On success, these functions return the inverse hyperbolic tangent of
x is a NaN, a NaN is returned.
x is +0 (-0), +0 (-0) is returned.
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:
xless than -1 or greater than +1
errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised.
xis +1 or -1
errno is set to ERANGE (but see BUGS). A divide-by-zero floating-point exception (FE_DIVBYZERO) is raised.
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 as set to EDOM instead of the POSIX-mandated ERANGE. Since version 2.10, glibc does the right thing.
This page is part of release 5.10 of the Linux
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