# acosl(3) [freebsd man page]

```ACOS(3) 						   BSD Library Functions Manual 						   ACOS(3)

NAME
acos, acosf, acosl -- arc cosine functions

LIBRARY
Math Library (libm, -lm)

SYNOPSIS
#include <math.h>

double
acos(double x);

float
acosf(float x);

long double
acosl(long double x);

DESCRIPTION
The acos(), acosf(), and acosl() functions compute the principal value of the arc cosine of x.

RETURN VALUES
These functions return the arc cosine in the range [0, pi] radians.  If:

|x| > 1,

acos(x) raises an invalid exception and returns an NaN.

asin(3), atan(3), atan2(3), cos(3), cosh(3), fenv(3), math(3), sin(3), sinh(3), tan(3), tanh(3)

STANDARDS
The acos(), acosf(), and acosl() functions conform to ISO/IEC 9899:1999 (``ISO C99'').

BSD								   July 31, 2008							       BSD```

## Check Out this Related Man Page

```ACOS(3) 						   BSD Library Functions Manual 						   ACOS(3)

NAME
acos -- arc cosine function

SYNOPSIS
#include <math.h>

double
acos(double x);

long double
acosl(long double x);

float
acosf(float x);

DESCRIPTION
The acos() function computes the principle value of the arc cosine of x.  The result is in the range [0, pi].

SPECIAL VALUES
acos(1) returns +0.

acos(x) returns a NAN and raises the "invalid" floating-point exception for |x| > 1.

VECTOR OPERATIONS
If you need to apply the acos() function to SIMD vectors or arrays, using the following functions provided by the Accelerate.framework may
give significantly better performance:

#include <Accelerate/Accelerate.h>

vFloat vacosf(vFloat x);
void vvacosf(float *y, const float *x, const int *n);
void vvacos(double *y, const double *x, const int *n);

sin(3), cos(3), tan(3), asin(3), atan(3), atan2(3), sinh(3), cosh(3), tanh(3), math(3)

STANDARDS
The acos() function conforms to ISO/IEC 9899:2011.

BSD								 December 11, 2006							       BSD```
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