# atanh(3) [linux man page]

ATANH(3) Linux Programmer's Manual ATANH(3)NAME

atanh, atanhf, atanhl - inverse hyperbolic tangent functionSYNOPSIS

#include <math.h> double atanh(double x); float atanhf(float x); long double atanhl(long double x); Link withFeature Test Macro Requirements for glibc (see feature_test_macros(7)): atanh(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc-lm.atanhf(), atanhl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; or cc-std=c99-std=c99DESCRIPTION

The atanh() function calculates the inverse hyperbolic tangent of x; that is the value whose hyperbolic tangent is x.RETURN VALUE

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, 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.-1ERRORS

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 thanor greater than +1 errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised. Pole error: x is +1 or-1errno is set to ERANGE (but see BUGS). A divide-by-zero floating-point exception (FE_DIVBYZERO) is raised.-1CONFORMING TO

C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.BUGS

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.SEE ALSO

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

This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2010-09-11 ATANH(3)

## Check Out this Related Man Page

ATANH(3) Linux Programmer's Manual ATANH(3)NAME

atanh, atanhf, atanhl - inverse hyperbolic tangent functionSYNOPSIS

#include <math.h> double atanh(double x); float atanhf(float x); long double atanhl(long double x); Link withFeature Test Macro Requirements for glibc (see feature_test_macros(7)): atanh(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or cc-lm.atanhf(), atanhl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc-std=c99-std=c99DESCRIPTION

The atanh() function calculates the inverse hyperbolic tangent of x; that is the value whose hyperbolic tangent is x.RETURN VALUE

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, 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.-1ERRORS

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 thanor greater than +1 errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised. Pole error: x is +1 or-1errno is set to ERANGE (but see BUGS). A divide-by-zero floating-point exception (FE_DIVBYZERO) is raised.-1CONFORMING TO

C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.BUGS

For a pole error, errno is set to EDOM; POSIX.1 says it should be set to ERANGE.SEE ALSO

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

This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2008-08-05 ATANH(3)