npm package: @stdlib/math-base-special-hacovercos
Description: Compute the half-value coversed cosine.
Author: The Stdlib Authors
Latest version: 0.3.1

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# Hacovercosine

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Compute the half-value [coversed cosine][coversed-cosine].

<section class="intro">

The half-value [coversed cosine][coversed-cosine] is defined as

<!-- <equation class="equation" label="eq:hacovercosine" align="center" raw="\operatorname{hacovercos}(\theta) = \frac{1 + \sin \theta}{2}" alt="Half-value coversed cosine."> -->

<div class="equation" align="center" data-raw-text="\operatorname{hacovercos}(\theta) = \frac{1 + \sin \theta}{2}" data-equation="eq:hacovercosine">
    <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@bb29798906e119fcb2af99e94b60407a270c9b32/lib/node_modules/@stdlib/math/base/special/hacovercos/docs/img/equation_hacovercosine.svg" alt="Half-value coversed cosine.">
    <br>
</div>

<!-- </equation> -->

</section>

<!-- /.intro -->

<section class="installation">

## Installation

```bash
npm install @stdlib/math-base-special-hacovercos
```

</section>

<section class="usage">

## Usage

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

#### hacovercos( x )

Computes the half-value [coversed cosine][coversed-cosine] (in radians).

```javascript
var v = hacovercos( 0.0 );
// returns 0.5

v = hacovercos( 3.141592653589793/2.0 );
// returns 1.0

v = hacovercos( -3.141592653589793/6.0 );
// returns 0.25
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var uniform = require( '@stdlib/random-array-uniform' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var TWO_PI = require( '@stdlib/constants-float64-two-pi' );
var hacovercos = require( '@stdlib/math-base-special-hacovercos' );

var opts = {
    'dtype': 'float64'
};
var x = uniform( 100, 0.0, TWO_PI, opts );

logEachMap( 'hacovercos(%0.4f) = %0.4f', x, hacovercos );
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/math/base/special/hacovercos.h"
```

#### stdlib_base_hacovercos( x )

Computes the half-value [coversed cosine][coversed-cosine] (in radians).

```c
double out = stdlib_base_hacovercos( 0.0 );
// returns 0.5

out = stdlib_base_hacovercos( 3.141592653589793 / 2.0 );
// returns 1.0
```

The function accepts the following arguments:

-   **x**: `[in] double` input value.

```c
double stdlib_base_hacovercos( const double x );
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

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

int main( void ) {
    const double x[] = { 0.0, 0.523, 0.785, 1.047, 3.14 };

    double y;
    int i;
    for ( i = 0; i < 5; i++ ) {
        y = stdlib_base_hacovercos( x[ i ] );
        printf( "hacovercos(%lf) = %lf\n", x[ i ], y );
    }
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/math-base/special/hacoversin`][@stdlib/math/base/special/hacoversin]</span><span class="delimiter">: </span><span class="description">compute the half-value coversed sine.</span>
-   <span class="package-name">[`@stdlib/math-base/special/havercos`][@stdlib/math/base/special/havercos]</span><span class="delimiter">: </span><span class="description">compute the half-value versed cosine.</span>

</section>

<!-- /.related -->

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].

#### Community

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---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/math-base-special-hacovercos/main/LICENSE

[coversed-cosine]: https://en.wikipedia.org/wiki/Versine

<!-- <related-links> -->

[@stdlib/math/base/special/hacoversin]: https://www.npmjs.com/package/@stdlib/math-base-special-hacoversin

[@stdlib/math/base/special/havercos]: https://www.npmjs.com/package/@stdlib/math-base-special-havercos

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</section>

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