# _ATAN2

Revision as of 17:14, 14 November 2015 by imported>Clippy

The **_ATAN2** function returns the radian angle between the positive x-axis of a plane and the point given by the coordinates (x, y) on it.

## Syntax

- angle! =
**_ATAN2(***y*,*x***)**

- angle! =

## Parameters

*y*is the vertical axis position(row) as a floating point value.*x*is the horizontal axis position(column) as a floating point value.

## Description

- The DOUBLE radian angle returned is positive for counter-clockwise angles (upper half-plane, y > 0).
- The DOUBLE radian angle returned is negative for clockwise angles (lower half-plane, y < 0).
- _ATAN2(y, x) = ATN(y / x) when x > 0
- _ATAN2(y, x) = ATN(y / x) + _PI when x < 0 and y >= 0
- _ATAN2(y, x) = ATN(y / x) - _PI when x < 0 and y < 0
- _ATAN2(y' x) = _PI / 2 when x = 0 and y > 0
- _ATAN2(y, x) = -_PI / 2 when x = 0 and y < 0
- _ATAN2(0, 0) is undefined and the function returns 0.

### Errors

## See also

- ATN (arctangent)
- _PI (QB64 constant value)
- Mathematical Operations

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