# Function Reference

# ATan

Calculates the arctangent of a number.

ATan ( expression )

## Parameters

expression | Any valid numeric expression.

## Return Value

Returns the trigonometric arctangent of the number. Result is in radians.

## Remarks

The result of 4 * ATan(1) is pi.

## Related

ACos, ASin, Cos, Sin, Tan

## Example

### Example 1

    #include <MsgBoxConstants.au3>

    Example()

    Func Example()
        ; Assign a Local variable the arcTangent of 0.5.
        Local $fArcTan1 = ATan(0.5)

        ; Display the result.
        MsgBox($MB_SYSTEMMODAL, "", $fArcTan1 & " rad.")

        ; Assign a Local constant variable the approximate PI number.
        Local Const $PI = 3.141592653589793

        ; Assign a Local variable the formula to switch from radian to degree (equals to one radian in degree).
        Local $fRadToDeg = 180 / $PI

        ; Assign a Local variable a number in degree.
        Local $fArcTan2 = $fRadToDeg * ATan(1)

        ; Display the result.
        MsgBox($MB_SYSTEMMODAL, "", $fArcTan2 & " deg.")
    EndFunc   ;==>Example

### Example 2

    ; Example of using ATan with degrees

    #include <Math.au3>
    #include <MsgBoxConstants.au3>

    Local $fDegree = _Degree(ATan(1))

    MsgBox($MB_SYSTEMMODAL, Default, "ATan(1) = " & $fDegree & " degrees")