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IMO 2009 — Complete Shortlist Question 20

IMO Shortlist · IMO 2009 — Complete Shortlist

Question 20

Let $P$ be a polygon that is convex and symmetric to some point $O$. Prove that for some parallelogram $R$ satisfying $P \subset R$ we have

$$
\frac{|R|}{|P|} \leq \sqrt{2}
$$

where $|R|$ and $|P|$ denote the area of the sets $R$ and $P$, respectively.