# atan2 - perldoc - phpman

    atan2 Y,X
            Returns the arctangent of Y/X in the range -PI to PI.

            For the tangent operation, you may use the "[Math::Trig::tan](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3ATrig%3A%3Atan/markdown)"
            function, or use the familiar relation:

                sub tan { sin($_[0]) / cos($_[0])  }

            The return value for "atan2(0,0)" is implementation-defined;
            consult your [atan2(3)](https://www.chedong.com/phpMan.php/man/atan2/3/markdown) manpage for more information.

            Portability issues: "atan2" in perlport.