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MathNet 2017-part-02 — 176 problems (EN–VI) Question 104

Math Olympiad Vault · MathNet 2017-part-02 — 176 problems (EN–VI)

Question 104

Let $ABC$ be a triangle with $AB = AC \ne BC$ and let $I$ be its incenter. The line $BI$ meets $AC$ at $D$, and the line through $D$ perpendicular to $AC$ meets $AI$ at $E$. Prove that the reflection of $I$ in $AC$ lies on the circumcircle of triangle $BDE$.