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MathNet 2004 — Part 02 Question 93

Math Olympiad Vault · MathNet 2004 — Part 02

Question 93

The incircle of $\triangle ABC$ with center $I$ touches the sides $AB$ and $AC$ at points $P$ and $Q$, respectively. $BI$ and $CI$ intersect $PQ$ at $K$ and $L$, respectively. Prove that circumcircle of $\triangle ILK$ touches the incircle of $\triangle ABC$ if and only if $AB + AC = 3BC$.