# Futurebasic/Language/Reference/atn

(Redirected from Futurebasic/language/reference/atn)

## Atn Edit

### Function Edit

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### Syntax Edit

radianAngle# = atn( expr )

### Description Edit

Returns the arctangent of

in radians. In other words, if *expr*

represents the tangent of some angle, then *expr*`atn`

`(`

*expr*`)`

returns the angle. The returned angle will be in the range of -π/2 to +π/2 radians (which corresponds to -90 to +90 degrees). `atn`

always returns a double-precision result.

### Example Edit

Because `atn`

`(1)`

equals π/4, you can use `atn`

to get a value for π.

dim pi# end globals pi = atn( 1 ) * 4 print pi

Program output:

3.14159265359

### Notes Edit

No special notes.