atanh(3) - f38

1atanh(3)                   Library Functions Manual                   atanh(3)
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NAME

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

9       Math library (libm, -lm)
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SYNOPSIS

12       #include <math.h>
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14       double atanh(double x);
15       float atanhf(float x);
16       long double atanhl(long double x);
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18   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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20       atanh():
21           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
22               || _XOPEN_SOURCE >= 500
23               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
24               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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26       atanhf(), atanhl():
27           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
28               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
29               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

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

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

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

64       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
65       tributes(7).
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67       ┌────────────────────────────────────────────┬───────────────┬─────────┐
68       │Interface                                   │ Attribute     │ Value   │
69       ├────────────────────────────────────────────┼───────────────┼─────────┤
70       │atanh(), atanhf(), atanhl()                 │ Thread safety │ MT-Safe │
71       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

74       C11, POSIX.1-2008.
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HISTORY

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

82       In  glibc  2.9  and  earlier, when a pole error occurs, errno is set to
83       EDOM instead of the POSIX-mandated ERANGE.   Since  glibc  2.10,  glibc
84       does the right thing.
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