ATAN2(3) Linux Programmer's Manual ATAN2(3)
**NAME**
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)**
June 8, 1993 1