Compute the cosine of a number.
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> Compute the [cosine][cosine] of a number.
``bash`
npm install @stdlib/math-base-special-cos
`javascript`
var cos = require( '@stdlib/math-base-special-cos' );
#### cos( x )
Computes the [cosine][cosine] of a number (in radians).
`javascript
var v = cos( 0.0 );
// returns 1.0
v = cos( 3.141592653589793/4.0 );
// returns ~0.707
v = cos( -3.141592653589793/6.0 );
// returns ~0.866
v = cos( NaN );
// returns NaN
`
`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 cos = require( '@stdlib/math-base-special-cos' );
var opts = {
'dtype': 'float64'
};
var x = uniform( 100, 0.0, TWO_PI, opts );
logEachMap( 'cos(%0.4f) = %0.4f', x, cos );
`
*
`c`
#include "stdlib/math/base/special/cos.h"
#### stdlib_base_cos( x )
Computes the [cosine][cosine] of a number (in radians).
`c
double out = stdlib_base_cos( 0.0 );
// returns 1.0
out = stdlib_base_cos( 3.141592653589793 / 4.0 );
// returns ~0.707
`
The function accepts the following arguments:
- x: [in] double input value.
`c`
double stdlib_base_cos( const double x );
`c
#include "stdlib/math/base/special/cos.h"
#include
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_cos( x[ i ] );
printf( "cos(%lf) = %lf\n", x[ i ], y );
}
}
`
*
- [@stdlib/math-base/special/cospi][@stdlib/math/base/special/cospi]: compute cos(πx).
- [@stdlib/math-base/special/cosm1][@stdlib/math/base/special/cosm1]: compute the cosine of a number minus one.
- [@stdlib/math-base/special/sin][@stdlib/math/base/special/sin]: compute the sine of a number.
- [@stdlib/math-base/special/tan][@stdlib/math/base/special/tan]: evaluate the tangent of a number.
*
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].
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---
Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
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[stdlib]: https://github.com/stdlib-js/stdlib
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[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-cos/tree/deno
[deno-readme]: https://github.com/stdlib-js/math-base-special-cos/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/math-base-special-cos/tree/umd
[umd-readme]: https://github.com/stdlib-js/math-base-special-cos/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/math-base-special-cos/tree/esm
[esm-readme]: https://github.com/stdlib-js/math-base-special-cos/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/math-base-special-cos/blob/main/branches.md
[cosine]: https://en.wikipedia.org/wiki/Cosine
[@stdlib/math/base/special/cospi]: https://www.npmjs.com/package/@stdlib/math-base-special-cospi
[@stdlib/math/base/special/cosm1]: https://www.npmjs.com/package/@stdlib/math-base-special-cosm1
[@stdlib/math/base/special/sin]: https://www.npmjs.com/package/@stdlib/math-base-special-sin
[@stdlib/math/base/special/tan]: https://www.npmjs.com/package/@stdlib/math-base-special-tan