=over =item atan2 Y,X X<atan2> X<arctangent> X<tan> X<tangent> Returns the arctangent of Y/X in the range -PI to PI. For the tangent operation, you may use the L<C<Math::Trig::tan>|Math::Trig/B<tan>> function, or use the familiar relation: sub tan { sin($_[0]) / cos($_[0]) } The return value for C<atan2(0,0)> is implementation-defined; consult your L<atan2(3)> manpage for more information. Portability issues: L<perlport/atan2>. =back