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man:acosl

ACOS(3) Linux Programmer's Manual ACOS(3)

NAME

`     acos, acosf, acosl - arc cosine function`

SYNOPSIS

`     #include <math.h>`
```     double acos(double x);
float acosf(float x);
long double acosl(long double x);```
`     Link with -lm.`
` Feature Test Macro Requirements for glibc (see feature_test_macros(7)):`
```     acosf(), acosl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE```

DESCRIPTION

```     These  functions calculate the arc cosine of x; that is the value whose
cosine is x.```

RETURN VALUE

```     On success, these functions return the arc cosine of x in radians;  the
return value is in the range [0, pi].```
`     If x is a NaN, a NaN is returned.`
`     If x is +1, +0 is returned.`
```     If  x is positive infinity or negative infinity, a domain error occurs,
and a NaN is returned.```
```     If x is outside the range [-1, 1], a domain error occurs, and a NaN  is
returned.```

ERRORS

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

ATTRIBUTES

```     For   an   explanation   of   the  terms  used  in  this  section,  see
attributes(7).```
```     allbox; lbw24 lb  lb  l  l  l.   Interface Attribute Value  T{  acos(),
acosf(), acosl() T}   Thread safety  MT-Safe```

CONFORMING TO

`     C99, POSIX.1-2001, POSIX.1-2008.`
`     The variant returning double also conforms to SVr4, 4.3BSD, C89.`

`     asin(3), atan(3), atan2(3), cacos(3), cos(3), sin(3), tan(3)`
```     This  page  is  part of release 4.16 of the Linux man-pages project.  A
`                                2017-09-15                           ACOS(3)`