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MathNet 2025 — 50 problems with figures (EN–VI) Question 37

Math Olympiad Vault · MathNet 2025 — 50 problems with figures (EN–VI)

Question 37

Right triangle $\triangle DEF$ with $\angle D = 90^{\circ}$ and $\angle F = 30^{\circ}$ is inscribed in equilateral triangle $\triangle ABC$ such that $D$, $E$, and $F$ lie on segments $\overline{BC}$, $\overline{CA}$, and $\overline{AB}$, respectively. Given that $BD = 7$ and $DC = 4$, compute $DE$.