1ACOSH(3P)                  POSIX Programmer's Manual                 ACOSH(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       acosh, acoshf, acoshl - inverse hyperbolic cosine functions
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SYNOPSIS

15       #include <math.h>
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17       double acosh(double x);
18       float acoshf(float x);
19       long double acoshl(long double x);
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DESCRIPTION

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

33       Upon  successful  completion,  these functions shall return the inverse
34       hyperbolic cosine of their argument.
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36       For finite values of x < 1, a domain error shall occur, and   either  a
37       NaN  (if  supported),  or  an  implementation-defined  value  shall  be
38       returned.
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40       If x is NaN, a NaN shall be returned.
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42       If x is +1, +0 shall be returned.
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44       If x is +Inf, +Inf shall be returned.
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46       If x is -Inf, a domain error shall occur, and either  a  NaN  (if  sup‐
47       ported), or an implementation-defined value shall be returned.
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ERRORS

50       These functions shall fail if:
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52       Domain Error
53              The x argument is finite and less than +1.0,  or is -Inf.
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55       If  the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
56       then  errno  shall  be  set  to  [EDOM].  If  the  integer   expression
57       (math_errhandling  &  MATH_ERREXCEPT)  is  non-zero,  then  the invalid
58       floating-point exception shall be raised.
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61       The following sections are informative.
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EXAMPLES

64       None.
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APPLICATION USAGE

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

72       None.
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FUTURE DIRECTIONS

75       None.
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SEE ALSO

78       cosh(), feclearexcept(), fetestexcept(), the Base Definitions volume of
79       IEEE Std 1003.1-2001,  Section  4.18, Treatment of Error Conditions for
80       Mathematical Functions, <math.h>
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83       Portions of this text are reprinted and reproduced in  electronic  form
84       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
85       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
86       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
87       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
88       event of any discrepancy between this version and the original IEEE and
89       The Open Group Standard, the original IEEE and The Open Group  Standard
90       is  the  referee document. The original Standard can be obtained online
91       at http://www.opengroup.org/unix/online.html .
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95IEEE/The Open Group                  2003                            ACOSH(3P)
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