# ATAN

Returns the arctangent of the input numeric expression as an angle, expressed in radians.

## Syntax

`ATAN(number)`

### Parameters

#### `number`

Numeric expression. If `null`, the function returns `null`.

## Examples

```esql
ROW a=12.9
| EVAL atan = ATAN(a)
```

Calculate the arctangent of the value `12.9` and store the result in a new column named `atan`.

```esql
ROW x=5.0, y=3.0
| EVAL atan_yx = ATAN(y / x)
```
