# @stdlib/math-base-special-acos

0.2.3 • Public • Published

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# acos

Compute the arccosine of a double-precision floating-point number.

## Installation

`npm install @stdlib/math-base-special-acos`

## Usage

`var acos = require( '@stdlib/math-base-special-acos' );`

#### acos( x )

Computes the arccosine of a double-precision floating-point number (in radians).

```var v = acos( 1.0 );
// returns 0.0

v = acos( 0.707 ); // ~pi/4
// returns ~0.7855

v = acos( 0.866 ); // ~pi/6
// returns ~0.5236

v = acos( NaN );
// returns NaN```

The domain of `x` is restricted to `[-1,1]`. If `|x| > 1`, the function returns `NaN`.

```var v = acos( -3.14 );
// returns NaN```

## Examples

```var linspace = require( '@stdlib/array-base-linspace' );
var acos = require( '@stdlib/math-base-special-acos' );

var x = linspace( -1.0, 1.0, 100 );

var i;
for ( i = 0; i < x.length; i++ ) {
console.log( acos( x[ i ] ) );
}```

## C APIs

### Usage

`#include "stdlib/math/base/special/acos.h"`

#### stdlib_base_acos( x )

Computes the arccosine of a double-precision floating-point number (in radians).

```double out = stdlib_base_acos( 1.0 );
// returns 0.0

out = stdlib_base_acos( 0.707 ); // ~pi/4
// returns ~0.7855```

The function accepts the following arguments:

• x: `[in] double` input value (in radians).
`double stdlib_base_acos( const double x );`

### Examples

```#include "stdlib/math/base/special/acos.h"
#include <stdio.h>

int main( void ) {
const double x[] = { -1.0, -0.78, -0.56, -0.33, -0.11, 0.11, 0.33, 0.56, 0.78, 1.0 };

double v;
int i;
for ( i = 0; i < 10; i++ ) {
v = stdlib_base_acos( x[ i ] );
printf( "acos(%lf) = %lf\n", x[ i ], v );
}
}```

## Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

## Package Sidebar

### Install

`npm i @stdlib/math-base-special-acos`

### Repository

github.com/stdlib-js/math-base-special-acos

stdlib.io

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