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MathNet 2026 — Part 03 Question 189

Math Olympiad Vault · MathNet 2026 — Part 03

Question 189

Inside a square $ABCD$ the equilateral triangle $ABE$ is built. Let $P$ be the intersection point of the lines $AC$ and $BE$. Let $F$ be the symmetric point of the $P$ with respect to the $DC$ line. It is requested to show that:
a) The triangle $CEF$ is equilateral.
b) The triangle $DEF$ is rectangle and isosceles.
c) The triangle $BDF$ is isosceles.
d) The triangle $PDF$ is equilateral.