=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>.

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