---
title: "acos"
description: "Returns the arc cosine of number"
---

# acos

> Returns the arc cosine of number

**This function is used by Ignition's Expression language.**
## Description
Returns the arc cosine of number, which must be a number between -1 and 1. The results will be an angle expressed in radians in the range of 0.0 through pi.

## Syntax
`acos(number)`

### Parameters

| Type | Parameter | Description |
|---|---|---|
| Float | `number` | The number to get the arc cosine of. Must be a value between -1 and 1. |

### Results
**Float** - The arc cosine of the value provided.

## Examples
```python title="Code Snippet"
acos(.38) //returns 1.181
```