Math library (libm, -lm)
#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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
_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).
|atanh(), atanhf(), atanhl()||Thread safety||MT-Safe|
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)
acosh(3), asinh(3), catanh(3), cosh(3), sinh(3), tanh(3).
The man pages atanhf(3) and atanhl(3) are aliases of atanh(3).