---
title: math.asin() function
description: >
  `math.asin()` returns the arcsine of `x` in radians.
menu:
  flux_v0_ref:
    name: math.asin
    parent: math
    identifier: math/asin
weight: 101
---

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`math.asin()` returns the arcsine of `x` in radians.



##### Function type signature

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

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

## Parameters

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

`x` should be greater than -1 and less than 1. Otherwise the function will
return `NaN`.


## Examples

- [Return the arcsine of a value](#return-the-arcsine-of-a-value)
- [Use math.asin in map](#use-mathasin-in-map)

### Return the arcsine of a value

```js
import "math"

math.asin(x: 0.22)

```


### Use math.asin in map

```js
import "math"

data
    |> map(fn: (r) => ({r with _value: math.asin(x: r._value)}))

```

{{< expand-wrapper >}}
{{% expand "View example input and output" %}}

#### Input data

| _time                | *tag | _value                |
| -------------------- | ---- | --------------------- |
| 2021-01-01T00:00:00Z | t1   | -0.021800000000000003 |
| 2021-01-01T00:00:10Z | t1   | 0.1092                |
| 2021-01-01T00:00:20Z | t1   | 0.0735                |
| 2021-01-01T00:00:30Z | t1   | 0.1753                |
| 2021-01-01T00:00:40Z | t1   | 0.15230000000000002   |
| 2021-01-01T00:00:50Z | t1   | 0.0443                |

| _time                | *tag | _value               |
| -------------------- | ---- | -------------------- |
| 2021-01-01T00:00:00Z | t2   | 0.1985               |
| 2021-01-01T00:00:10Z | t2   | 0.0497               |
| 2021-01-01T00:00:20Z | t2   | -0.0375              |
| 2021-01-01T00:00:30Z | t2   | 0.1977               |
| 2021-01-01T00:00:40Z | t2   | 0.1386               |
| 2021-01-01T00:00:50Z | t2   | 0.018600000000000002 |


#### Output data

| _time                | _value                | *tag |
| -------------------- | --------------------- | ---- |
| 2021-01-01T00:00:00Z | -0.021801727074707577 | t1   |
| 2021-01-01T00:00:10Z | 0.10941820137571553   | t1   |
| 2021-01-01T00:00:20Z | 0.07356633896021608   | t1   |
| 2021-01-01T00:00:30Z | 0.17621047844966892   | t1   |
| 2021-01-01T00:00:40Z | 0.1528950055407725    | t1   |
| 2021-01-01T00:00:50Z | 0.044314502528968014  | t1   |

| _time                | _value               | *tag |
| -------------------- | -------------------- | ---- |
| 2021-01-01T00:00:00Z | 0.1998272282367503   | t2   |
| 2021-01-01T00:00:10Z | 0.04972048335509017  | t2   |
| 2021-01-01T00:00:20Z | -0.03750879462898862 | t2   |
| 2021-01-01T00:00:30Z | 0.19901105310181802  | t2   |
| 2021-01-01T00:00:40Z | 0.13904763050983682  | t2   |
| 2021-01-01T00:00:50Z | 0.0186010726429996   | t2   |

{{% /expand %}}
{{< /expand-wrapper >}}