npm package: @stdlib/math-base-special-havercosf
Description: Compute the half-value versed cosine of a single-precision floating-point number (in radians).
Author: The Stdlib Authors
Latest version: 0.1.1

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# Havercosine

[![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 [versed cosine][versed-cosine] of a single-precision floating-point number (in radians).

<section class="intro">

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

<!-- <equation class="equation" label="eq:havercosine" align="center" raw="\operatorname{havercos}(\theta) = \frac{1 + \cos \theta}{2}" alt="Haversed cosine."> -->

<!-- </equation> -->

</section>

<!-- /.intro -->

<section class="installation">

## Installation

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

</section>

<section class="usage">

## Usage

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

#### havercosf( x )

Computes the half-value [versed cosine][versed-cosine] of a single-precision floating-point number (in radians).

```javascript
var v = havercosf( 0.0 );
// returns 1.0

v = havercosf( 3.141592653589793/2.0 );
// returns 0.5

v = havercosf( -3.141592653589793/6.0 );
// returns ~0.9330
```

</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-float32-two-pi' );
var havercosf = require( '@stdlib/math-base-special-havercosf' );

var opts = {
    'dtype': 'float32'
};
var x = uniform( 100, 0.0, TWO_PI, opts );

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

</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/havercosf.h"
```

#### stdlib_base_havercosf( x )

Computes the half-value [versed cosine][versed-cosine] of a single-precision floating-point number (in radians).

```c
float out = stdlib_base_havercosf( 0.0f );
// returns 1.0f

out = stdlib_base_havercosf( 3.141592653589793f / 2.0f );
// returns 0.5f
```

The function accepts the following arguments:

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

```c
float stdlib_base_havercosf( const float 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/havercosf.h"
#include <stdio.h>

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

    float y;
    int i;
    for ( i = 0; i < 5; i++ ) {
        y = stdlib_base_havercosf( x[ i ] );
        printf( "havercosf(%f) = %f\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">

</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

[![Chat][chat-image]][chat-url]

---

## 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-havercosf/main/LICENSE

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

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</section>

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