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MathNet 2009-part-04 — 175 problems (EN–VI) Question 136

Math Olympiad Vault · MathNet 2009-part-04 — 175 problems (EN–VI)

Question 136

Prove that
$$
\frac{AO^2}{BC} + \frac{BO^2}{CA} + \frac{CO^2}{AB} \ge \frac{AO + BO + CO}{\sqrt{3}}
$$

where $O$ is the point inside triangle $ABC$ such that $\angle AOB = \angle BOC = \angle COA = 120^\circ$.