---
title: math.cos() function
description: >
  `math.cos()` returns the cosine of the radian argument `x`.
menu:
  flux_0_x_ref:
    name: math.cos
    parent: math
    identifier: math/cos
weight: 101
---

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`math.cos()` returns the cosine of the radian argument `x`.



##### Function type signature

```js
(x: float) => float
```

{{% caption %}}For more information, see [Function type signatures](/flux/v0.x/function-type-signatures/).{{% /caption %}}

## Parameters

### x
({{< req >}})
Value to operate on.




## Examples

### Use math.cos in map

```js
import "math"
import "sampledata"

sampledata.float()
    |> map(fn: (r) => ({_time: r._time, _value: math.cos(x: r._value)}))

```