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MathNet 2017-part-04 — 176 problems (EN–VI) Question 39

Math Olympiad Vault · MathNet 2017-part-04 — 176 problems (EN–VI)

Question 39

Let $ABC$ be a triangle with $\angle A = 90^{\circ}$ and let $D$ be the foot of the altitude from $A$. The midpoints of $AD$ and $AC$ are called $E$ and $F$, respectively. Let $M$ be the centre of the circumcircle of $\triangle BEF$. Prove that $AC \parallel BM$.