acos(3) - f38

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

6       acos, acosf, acosl - arc cosine 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 acos(double x);
15       float acosf(float x);
16       long double acosl(long double x);
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18   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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20       acosf(), acosl():
21           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
22               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
23               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

26       These  functions calculate the arc cosine of x; that is the value whose
27       cosine is x.
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RETURN VALUE

30       On success, these functions return the arc cosine of x in radians;  the
31       return value is in the range [0, pi].
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33       If x is a NaN, a NaN is returned.
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35       If x is +1, +0 is returned.
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37       If  x is positive infinity or negative infinity, a domain error occurs,
38       and a NaN is returned.
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40       If x is outside the range [-1, 1], a domain error occurs, and a NaN  is
41       returned.
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ERRORS

44       See  math_error(7) for information on how to determine whether an error
45       has occurred when calling these functions.
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47       The following errors can occur:
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49       Domain error: x is outside the range [-1, 1]
50              errno is set  to  EDOM.   An  invalid  floating-point  exception
51              (FE_INVALID) is raised.
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ATTRIBUTES

54       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
55       tributes(7).
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57       ┌────────────────────────────────────────────┬───────────────┬─────────┐
58       │Interface                                   │ Attribute     │ Value   │
59       ├────────────────────────────────────────────┼───────────────┼─────────┤
60       │acos(), acosf(), acosl()                    │ Thread safety │ MT-Safe │
61       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

64       C11, POSIX.1-2008.
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HISTORY

67       C99, POSIX.1-2001.
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69       The variant returning double also conforms to C89, SVr4, 4.3BSD.
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