=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 C<Math::Trig::tan>
function, or use the familiar relation:

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

Note that atan2(0, 0) is not well-defined.

=back