# ACOS¶

The **ACOS** function calculates the arccosine, or inverse cosine, (in radians) of the given value, which must be between -1 and 1.

## Usage¶

`acos(num) : num`

## Examples¶

The following example creates a single NOR row with a column x that calculates the arccosine of 0.5 resulting in an answer of 1.0472 (which is 60° in radians).

```
NORROWS 1 | CALC x asin(0.5)
```