(3.0.5 - 3.0.18 only, PHP 4 >= 4.0.0)

atan2 -- arc tangent of two variables

## Description

`float `**atan2**

(float y, float x)

This function calculates the arc tangent of the two variables
*x* and *y*. It is
similar to calculating the arc tangent of
*y* / *x*, except that
the signs of both arguments are used to determine the quadrant of
the result.

The function returns the result in radians, which is between -PI
and PI (inclusive).

See also **acos()** and **atan()**.