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

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

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

43       See  math_error(7) for information on how to determine whether an error
44       has occurred when calling these functions.
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46       The following errors can occur:
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48       Domain error: x less than -1 or greater than +1
49              errno is set  to  EDOM.   An  invalid  floating-point  exception
50              (FE_INVALID) is raised.
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52       Pole error: x is +1 or -1
53              errno  is set to ERANGE.  A divide-by-zero floating-point excep‐
54              tion (FE_DIVBYZERO) is raised.
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CONFORMING TO

57       C99, POSIX.1-2001.  The variant returning double also conforms to SVr4,
58       4.3BSD, C89.
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SEE ALSO

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

64       This  page  is  part of release 3.25 of the Linux man-pages project.  A
65       description of the project, and information about reporting  bugs,  can
66       be found at http://www.kernel.org/doc/man-pages/.
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70                                  2008-08-05                          ATANH(3)
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