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https://github.com/stdlib-js/math-base-special-kernel-cos
Compute the cosine of a number on `[-π/4, π/4]`.
https://github.com/stdlib-js/math-base-special-kernel-cos
angle cos cosine javascript kernel math mathematics node node-js nodejs radians stdlib trig trigonometry
Last synced: 4 days ago
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Compute the cosine of a number on `[-π/4, π/4]`.
- Host: GitHub
- URL: https://github.com/stdlib-js/math-base-special-kernel-cos
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-07T17:35:07.000Z (over 3 years ago)
- Default Branch: main
- Last Pushed: 2024-10-01T10:49:18.000Z (about 1 month ago)
- Last Synced: 2024-10-02T06:23:14.465Z (about 1 month ago)
- Topics: angle, cos, cosine, javascript, kernel, math, mathematics, node, node-js, nodejs, radians, stdlib, trig, trigonometry
- Language: JavaScript
- Size: 469 KB
- Stars: 2
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
- Citation: CITATION.cff
- Security: SECURITY.md
Awesome Lists containing this project
README
About stdlib...
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When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.
To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!
# kernelCos
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Compute the [cosine][cosine] of a double-precision floating-point number on `[-π/4, π/4]`.
## Installation
```bash
npm install @stdlib/math-base-special-kernel-cos
```
Alternatively,
- To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).
- If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).
- For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).
The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.
To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.
## Usage
```javascript
var kernelCos = require( '@stdlib/math-base-special-kernel-cos' );
```
#### kernelCos( x, y )
Computes the [cosine][cosine] of a double-precision floating-point number on `[-π/4, π/4]`.
```javascript
var v = kernelCos( 0.0, 0.0 );
// returns ~1.0
v = kernelCos( 3.141592653589793/6.0, 0.0 );
// returns ~0.866
v = kernelCos( 0.785, -1.144e-17 );
// returns ~0.707
v = kernelCos( NaN, 0.0 );
// returns NaN
```
## Notes
- For increased accuracy, the number for which the [cosine][cosine] should be evaluated can be supplied as a [double-double number][double-double-arithmetic] (i.e., a non-evaluated sum of two [double-precision floating-point numbers][ieee754] `x` and `y`).
- As components of a [double-double number][double-double-arithmetic], the two [double-precision floating-point numbers][ieee754] `x` and `y` must satisfy
where `ulp` stands for [units in the last place][ulp].
## Examples
```javascript
var linspace = require( '@stdlib/array-base-linspace' );
var PI = require( '@stdlib/constants-float64-pi' );
var kernelCos = require( '@stdlib/math-base-special-kernel-cos' );
var x = linspace( -PI/4.0, PI/4.0, 100 );
var i;
for ( i = 0; i < x.length; i++ ) {
console.log( 'kernelCos(%d) = %d', x[ i ], kernelCos( x[ i ], 0.0 ) );
}
```
* * *
## C APIs
### Usage
```c
#include "stdlib/math/base/special/kernel_cos.h"
```
#### stdlib_base_kernel_cos( x, y )
Computes the [cosine][cosine] of a double-precision floating-point number on `[-π/4, π/4]`.
```c
var v = stdlib_base_kernel_cos( 0.0, 0.0 );
// returns ~0.0
v = stdlib_base_kernel_cos( 3.141592653589793/6.0, 0.0 );
// returns ~0.866
```
The function accepts the following arguments:
- **x**: `[in] double` input value (in radians, assumed to be bounded by `~pi/4` in magnitude).
- **y**: `[in] double` tail of `x`.
```c
double stdlib_base_kernel_cos( const double x, const double y );
```
### Notes
- For increased accuracy, the number for which the [cosine][cosine] should be evaluated can be supplied as a [double-double number][double-double-arithmetic] (i.e., a non-evaluated sum of two [double-precision floating-point numbers][ieee754] `x` and `y`).
### Examples
```c
#include "stdlib/math/base/special/kernel_cos.h"
#include
int main( void ) {
const double x[] = { -0.7853981633974483, -0.6108652381980153, -0.4363323129985824, -0.26179938779914946, -0.08726646259971649, 0.08726646259971649, 0.26179938779914935, 0.43633231299858233, 0.6108652381980153, 0.7853981633974483 };
double out;
int i;
for ( i = 0; i < 10; i++ ) {
out = stdlib_base_kernel_cos( x[ i ], 0.0 );
printf ( "x[ i ]: %lf, y: %lf, out: %lf\n", x[ i ], 0.0, out );
}
}
```
* * *
## See Also
- [`@stdlib/math-base/special/cos`][@stdlib/math/base/special/cos]: compute the cosine of a number.
- [`@stdlib/math-base/special/kernel-sin`][@stdlib/math/base/special/kernel-sin]: compute the sine of a double-precision floating-point number on \[-π/4, π/4].
- [`@stdlib/math-base/special/kernel-tan`][@stdlib/math/base/special/kernel-tan]: compute the tangent of a double-precision floating-point number on \[-π/4, π/4].
* * *
## 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]
---
## Copyright
Copyright © 2016-2024. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/math-base-special-kernel-cos.svg
[npm-url]: https://npmjs.org/package/@stdlib/math-base-special-kernel-cos
[test-image]: https://github.com/stdlib-js/math-base-special-kernel-cos/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/math-base-special-kernel-cos/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/math-base-special-kernel-cos/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/math-base-special-kernel-cos?branch=main
[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg
[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im
[stdlib]: https://github.com/stdlib-js/stdlib
[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors
[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules
[deno-url]: https://github.com/stdlib-js/math-base-special-kernel-cos/tree/deno
[deno-readme]: https://github.com/stdlib-js/math-base-special-kernel-cos/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/math-base-special-kernel-cos/tree/umd
[umd-readme]: https://github.com/stdlib-js/math-base-special-kernel-cos/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/math-base-special-kernel-cos/tree/esm
[esm-readme]: https://github.com/stdlib-js/math-base-special-kernel-cos/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/math-base-special-kernel-cos/blob/main/branches.md
[cosine]: https://en.wikipedia.org/wiki/Cosine
[double-double-arithmetic]: https://en.wikipedia.org/wiki/Quadruple-precision_floating-point_format#Double-double_arithmetic
[ieee754]: https://en.wikipedia.org/wiki/IEEE_floating_point
[ulp]: https://en.wikipedia.org/wiki/Unit_in_the_last_place
[@stdlib/math/base/special/cos]: https://github.com/stdlib-js/math-base-special-cos
[@stdlib/math/base/special/kernel-sin]: https://github.com/stdlib-js/math-base-special-kernel-sin
[@stdlib/math/base/special/kernel-tan]: https://github.com/stdlib-js/math-base-special-kernel-tan