1ACOS(3) Linux Programmer's Manual ACOS(3)
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6 acos, acosf, acosl - arc cosine function
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9 #include <math.h>
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11 double acos(double x);
12 float acosf(float x);
13 long double acosl(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 acosf(), acosl():
20 _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
21 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
22 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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25 These functions calculate the arc cosine of x; that is the value whose
26 cosine is x.
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29 On success, these functions return the arc cosine of x in radians; the
30 return value is in the range [0, pi].
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32 If x is a NaN, a NaN is returned.
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34 If x is +1, +0 is returned.
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36 If x is positive infinity or negative infinity, a domain error occurs,
37 and a NaN is returned.
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39 If x is outside the range [-1, 1], a domain error occurs, and a NaN is
40 returned.
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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 is outside the range [-1, 1]
49 errno is set to EDOM. An invalid floating-point exception
50 (FE_INVALID) is raised.
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53 For an explanation of the terms used in this section, see
54 attributes(7).
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56 ┌─────────────────────────┬───────────────┬─────────┐
57 │Interface │ Attribute │ Value │
58 ├─────────────────────────┼───────────────┼─────────┤
59 │acos(), acosf(), acosl() │ Thread safety │ MT-Safe │
60 └─────────────────────────┴───────────────┴─────────┘
62 C99, POSIX.1-2001, POSIX.1-2008.
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64 The variant returning double also conforms to SVr4, 4.3BSD, C89.
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67 asin(3), atan(3), atan2(3), cacos(3), cos(3), sin(3), tan(3)
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70 This page is part of release 5.07 of the Linux man-pages project. A
71 description of the project, information about reporting bugs, and the
72 latest version of this page, can be found at
73 https://www.kernel.org/doc/man-pages/.
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77 2017-09-15 ACOS(3)