@nataliapc/mcp-openmsx/resources/programming/basic_wiki/ATN().md

Model context protocol server for openMSX automation and control

# ATN()

## Effect

Returns the arctangent of a variable.

## Syntax

`ATN(<Number>)`

## Parameter

`<Number>` can be a value, a numeric variable or an expression.

## Example

```basic
10 PRINT "The arctangent of 1 is ";ATN(1)
20 PRINT "The arctangent of -1.23 is ";ATN(-1.23)
 
RUN
The arctangent of 1 is .78539816339745
The arctangent of -1.23 is .88817377437769
```

## Related to

`COS()`, `SIN()`, `TAN()`

## Compatibility

MSX-BASIC 1.0 or higher

## Source

Retrieved from "https://www.msx.org/wiki/ATN()"