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# Function cos

Calculate the cosine of a value.

For matrices, the function is evaluated element wise.


## Syntax

```js
math.cos(x)
```

### Parameters

Parameter | Type | Description
--------- | ---- | -----------
`x` | number &#124; BigNumber &#124; Complex &#124; Unit &#124; Array &#124; Matrix | Function input

### Returns

Type | Description
---- | -----------
number &#124; BigNumber &#124; Complex &#124; Array &#124; Matrix | Cosine of x


### Throws

Type | Description
---- | -----------


## Examples

```js
math.cos(2)                      // returns number -0.4161468365471422
math.cos(math.pi / 4)            // returns number  0.7071067811865475
math.cos(math.unit(180, 'deg'))  // returns number -1
math.cos(math.unit(60, 'deg'))   // returns number  0.5

const angle = 0.2
math.pow(math.sin(angle), 2) + math.pow(math.cos(angle), 2) // returns number ~1
```


## See also

[cos](cos.md),
[tan](tan.md)