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

NAME atanh, atanhf, atanhl - inverse hyperbolic tangent function

SYNOPSIS #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)):

atanh(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or cc -std=c99 atanhf(), atanhl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99

DESCRIPTION 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 -1, a pole error occurs, and the functions return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with the mathemati- cally correct sign.

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

ERRORS 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. A divide-by-zero floating-point excep- tion (FE_DIVBYZERO) is raised.

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