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MathNet 2025-part-02 — 186 problems (EN–VI) Question 17

Math Olympiad Vault · MathNet 2025-part-02 — 186 problems (EN–VI)

Question 17

Let $ABC$ be a right isosceles triangle with right angle at $A$, $O$ the midpoint of the hypotenuse $BC$, $E$ the midpoint of the segment $CO$, $M$ the midpoint of $AC$, and $D$ the midpoint of $AM$. Let $F$ be the intersection of lines $OD$ and $AE$.

a) Prove that $MF \perp OD$.

Question illustration

b) Prove that $FC = OC$.