atan2 - arc tangent function of two variables

## SYNOPSIS

**#include** **<math.h>**
**double** **atan2(double** *y***,** **double** *x***);**

## DESCRIPTION

The **atan2()** 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.

## RETURN VALUE

The **atan2()** function returns the result in radians, which
is between -PI and PI (inclusive).

## CONFORMING TO

SVID 3, POSIX, BSD 4.3, ISO 9899

## SEE ALSO

**acos(3)**, **asin(3)**, **atan(3)**, **cos(3)**, **sin(3)**, **tan(3)**