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MathNet 2000 — Math Olympiad Vault Question 40

Math Olympiad Vault · MathNet 2000 — Math Olympiad Vault

Question 40

Given a triangle $A B C$ with $\angle A=120^\circ$. The points $K$ and $L$ lie on the sides $A B$ and $A C$, respectively. Let $B K P$ and $C L Q$ be equilateral triangles constructed outside the triangle $A B C$. Prove that
$$
|P Q| \geqslant \frac{\sqrt{3}}{2} \cdot (|A B|+|A C|) .
$$