1ATANH(3)                   Linux Programmer's Manual                  ATANH(3)
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NAME

6       atanh, atanhf, atanhl - inverse hyperbolic tangent function
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SYNOPSIS

9       #include <math.h>
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11       double atanh(double x);
12       float atanhf(float x);
13       long double atanhl(long double x);
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15       Link with -lm.
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17   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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19       atanh():
20           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
21           _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
22           _POSIX_C_SOURCE >= 200112L;
23           or cc -std=c99
24       atanhf(), atanhl():
25           _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
26           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
27           or cc -std=c99
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DESCRIPTION

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

34       On success, these functions return the inverse hyperbolic tangent of x.
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36       If x is a NaN, a NaN is returned.
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38       If x is +0 (-0), +0 (-0) is returned.
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40       If  x  is  +1  or  -1,  a  pole  error occurs, and the functions return
41       HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively,  with  the  mathemati‐
42       cally correct sign.
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44       If  the  absolute  value of x is greater than 1, a domain error occurs,
45       and a NaN is returned.
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ERRORS

48       See math_error(7) for information on how to determine whether an  error
49       has occurred when calling these functions.
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51       The following errors can occur:
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53       Domain error: x less than -1 or greater than +1
54              errno  is  set  to  EDOM.   An  invalid floating-point exception
55              (FE_INVALID) is raised.
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57       Pole error: x is +1 or -1
58              errno is set to ERANGE (but see BUGS).  A divide-by-zero  float‐
59              ing-point exception (FE_DIVBYZERO) is raised.
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CONFORMING TO

62       C99, POSIX.1-2001.  The variant returning double also conforms to SVr4,
63       4.3BSD, C89.
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BUGS

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

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

74       This page is part of release 3.53 of the Linux  man-pages  project.   A
75       description  of  the project, and information about reporting bugs, can
76       be found at http://www.kernel.org/doc/man-pages/.
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80                                  2010-09-11                          ATANH(3)
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