Question 12
In convex quadrilateral $ABCD,$ $\angle A \cong \angle C,$ $AB = CD = 180,$ and $AD \ne BC.$ The perimeter of $ABCD$ is $640.$ Find $\lfloor 1000 \cos A \rfloor.$ (The notation $\lfloor x \rfloor$ means the greatest integer that is less than or equal to $x.$)