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MathNet 2023-part-06 — 191 problems (EN–VI) Question 156

Math Olympiad Vault · MathNet 2023-part-06 — 191 problems (EN–VI)

Question 156

Let $ABC$ be a triangle and $D$, $E$ be points on segments $AB$, $AC$ respectively, such that $DE \parallel BC$. Let the circumcircle of $ABC$ meet the circumcircles of $BDE$ and $CDE$ again at $K$, $L$ respectively. Let $T$ be the intersection of the lines $BK$ and $CL$. Prove that $TA$ is tangent to the circumcircle of $ABC$.