1ATANH(P)                   POSIX Programmer's Manual                  ATANH(P)
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NAME

6       atanh, atanhf, atanhl - inverse hyperbolic tangent functions
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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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DESCRIPTION

17       These  functions  shall compute the inverse hyperbolic tangent of their
18       argument x.
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20       An application wishing to check for error situations should  set  errno
21       to  zero  and  call  feclearexcept(FE_ALL_EXCEPT)  before calling these
22       functions.  On return, if errno is non-zero or  fetestexcept(FE_INVALID
23       |  FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
24       occurred.
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RETURN VALUE

27       Upon successful completion, these functions shall  return  the  inverse
28       hyperbolic tangent of their argument.
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30       If  x  is  ±1,  a  pole  error  shall occur, and atanh(), atanhf(), and
31       atanhl() shall return the value of the macro HUGE_VAL,  HUGE_VALF,  and
32       HUGE_VALL, respectively, with the same sign as the correct value of the
33       function.
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35       For finite |x|>1, a domain error shall occur, and    either a  NaN  (if
36       supported), or   an implementation-defined value shall be returned.
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38       If x is NaN, a NaN shall be returned.
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40       If x is ±0, x shall be returned.
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42       If  x  is  ±Inf,  a domain error shall occur, and either a NaN (if sup‐
43       ported), or an implementation-defined value shall be returned.
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45       If x is subnormal, a range error may occur and x should be returned.
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ERRORS

48       These functions shall fail if:
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50       Domain Error
51              The x argument is finite and not in the range [-1,1],     or  is
52              ±Inf.
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54       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
55       then  errno  shall  be  set  to  [EDOM].  If  the  integer   expression
56       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then  the invalid
57       floating-point exception shall be raised.
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59       Pole Error
60              The x argument is ±1.
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62       If the integer expression (math_errhandling & MATH_ERRNO) is  non-zero,
63       then  errno  shall  be  set  to  [ERANGE].  If  the  integer expression
64       (math_errhandling & MATH_ERREXCEPT) is non-zero,  then  the  divide-by-
65       zero floating-point exception shall be raised.
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69       These functions may fail if:
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71       Range Error
72              The value of x is subnormal.
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74       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
75       then errno  shall  be  set  to  [ERANGE].  If  the  integer  expression
76       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero, then the underflow
77       floating-point exception shall be raised.
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80       The following sections are informative.
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EXAMPLES

83       None.
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APPLICATION USAGE

86       On  error,  the  expressions  (math_errhandling   &   MATH_ERRNO)   and
87       (math_errhandling  & MATH_ERREXCEPT) are independent of each other, but
88       at least one of them must be non-zero.
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RATIONALE

91       None.
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FUTURE DIRECTIONS

94       None.
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SEE ALSO

97       feclearexcept() , fetestexcept() , tanh() , the Base Definitions volume
98       of  IEEE Std 1003.1-2001,  Section  4.18, Treatment of Error Conditions
99       for Mathematical Functions, <math.h>
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102       Portions of this text are reprinted and reproduced in  electronic  form
103       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
104       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
105       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
106       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
107       event of any discrepancy between this version and the original IEEE and
108       The Open Group Standard, the original IEEE and The Open Group  Standard
109       is  the  referee document. The original Standard can be obtained online
110       at http://www.opengroup.org/unix/online.html .
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114IEEE/The Open Group                  2003                             ATANH(P)
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