﻿---
title: ES|QL ACOS function
description: 
url: https://www.elastic.co/elastic/docs-builder/docs/2857/reference/query-languages/esql/functions-operators/math-functions/acos
products:
  - Elasticsearch
---

# ES|QL ACOS function
## Syntax

![Embedded](https://www.elastic.co/elastic/docs-builder/docs/2857/reference/query-languages/esql/images/functions/acos.svg)


## Parameters

<definitions>
  <definition term="number">
    Number between -1 and 1. If `null`, the function returns `null`.
  </definition>
</definitions>


## Description

Returns the [arccosine](https://en.wikipedia.org/wiki/Inverse_trigonometric_functions) of `n` as an angle, expressed in radians.

## Supported types


| number        | result |
|---------------|--------|
| double        | double |
| integer       | double |
| long          | double |
| unsigned_long | double |


## Example

```esql
ROW a=.9
| EVAL acos=ACOS(a)
```


| a:double | acos:double         |
|----------|---------------------|
| .9       | 0.45102681179626236 |