[Overview][Constants][Types][Classes][Procedures and functions][Index] | Reference for unit 'Math' (#rtl)

# ArcTan2

Return arctangent of (y/x)

## Declaration

Source position: math.pp line 361

`function ArcTan2(`
`y: Float;`
`x: Float`
`):Float;`

## Description

arctan2 calculates arctan(y/x), and returns an angle in the correct quadrant. The returned angle will be in the range $-\pi$ to $\pi$ radians. The values of x and y must be between -2\^{}64 and 2\^{}64, moreover x should be different from zero. On Intel systems this function is implemented with the native intel fpatan instruction.

## See also

arccos |  | Return inverse cosine
arcosh |  | Return inverse hyperbolic cosine
arsinh |  | Return inverse hyperbolic sine
artanh |  | Return inverse hyperbolic tangent

## Example

    Program Example6;

    { Program to demonstrate the arctan2 function. }

    Uses math;

      Procedure WriteRadDeg(X : float);

      begin
        Writeln(X:8:5,' rad = ',radtodeg(x):8:5,' degrees.')
      end;

    begin
      WriteRadDeg (arctan2(2,1));
    end.