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           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
21               || _XOPEN_SOURCE >= 500
22               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
23               || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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25       atanhf(), atanhl():
26           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
27               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
28               || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

31       These  functions calculate the inverse hyperbolic tangent of x; that is
32       the value whose hyperbolic tangent is x.
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RETURN VALUE

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

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

63       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
64       tributes(7).
65
66       ┌────────────────────────────────────────────┬───────────────┬─────────┐
67       │Interface                                   │ Attribute     │ Value   │
68       ├────────────────────────────────────────────┼───────────────┼─────────┤
69       │atanh(), atanhf(), atanhl()                 │ Thread safety │ MT-Safe │
70       └────────────────────────────────────────────┴───────────────┴─────────┘
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CONFORMING TO

73       C99, POSIX.1-2001, POSIX.1-2008.
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75       The variant returning double also conforms to SVr4, 4.3BSD.
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BUGS

78       In  glibc  2.9  and  earlier, when a pole error occurs, errno is set to
79       EDOM instead of the POSIX-mandated ERANGE.  Since version  2.10,  glibc
80       does the right thing.
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SEE ALSO

83       acosh(3), asinh(3), catanh(3), cosh(3), sinh(3), tanh(3)
84

COLOPHON

86       This  page  is  part of release 5.13 of the Linux man-pages project.  A
87       description of the project, information about reporting bugs,  and  the
88       latest     version     of     this    page,    can    be    found    at
89       https://www.kernel.org/doc/man-pages/.
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93                                  2021-03-22                          ATANH(3)
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