1COS(3P)                    POSIX Programmer's Manual                   COS(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.
10

NAME

12       cos, cosf, cosl — cosine function
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SYNOPSIS

15       #include <math.h>
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17       double cos(double x);
18       float cosf(float x);
19       long double cosl(long double x);
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DESCRIPTION

22       The functionality described on this reference page is aligned with  the
23       ISO C  standard.  Any  conflict between the requirements described here
24       and the ISO C standard is unintentional. This  volume  of  POSIX.1‐2017
25       defers to the ISO C standard.
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27       These  functions shall compute the cosine of their argument x, measured
28       in radians.
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30       An application wishing to check for error situations should  set  errno
31       to  zero  and  call  feclearexcept(FE_ALL_EXCEPT)  before calling these
32       functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
33       FE_DIVBYZERO  |  FE_OVERFLOW  | FE_UNDERFLOW) is non-zero, an error has
34       occurred.
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RETURN VALUE

37       Upon successful completion, these functions shall return the cosine  of
38       x.
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40       If x is NaN, a NaN shall be returned.
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42       If x is ±0, the value 1.0 shall be returned.
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44       If x is ±Inf, a domain error shall occur, and a NaN shall be returned.
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ERRORS

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

61   Taking the Cosine of a 45-Degree Angle
62           #include <math.h>
63           ...
64           double radians = 45 * M_PI / 180;
65           double result;
66           ...
67           result = cos(radians);
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APPLICATION USAGE

70       These  functions  may  lose accuracy when their argument is near an odd
71       multiple of π/2 or is far from 0.
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73       On  error,  the  expressions  (math_errhandling   &   MATH_ERRNO)   and
74       (math_errhandling  & MATH_ERREXCEPT) are independent of each other, but
75       at least one of them must be non-zero.
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RATIONALE

78       None.
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FUTURE DIRECTIONS

81       None.
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SEE ALSO

84       acos(), feclearexcept(), fetestexcept(), isnan(), sin(), tan()
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86       The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of
87       Error Conditions for Mathematical Functions, <math.h>
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90       Portions  of  this text are reprinted and reproduced in electronic form
91       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
92       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
93       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
94       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
95       event of any discrepancy between this version and the original IEEE and
96       The  Open Group Standard, the original IEEE and The Open Group Standard
97       is the referee document. The original Standard can be  obtained  online
98       at http://www.opengroup.org/unix/online.html .
99
100       Any  typographical  or  formatting  errors that appear in this page are
101       most likely to have been introduced during the conversion of the source
102       files  to  man page format. To report such errors, see https://www.ker‐
103       nel.org/doc/man-pages/reporting_bugs.html .
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107IEEE/The Open Group                  2017                              COS(3P)
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