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MathNet 2015-part-03 — 191 problems (EN–VI) Question 37

Math Olympiad Vault · MathNet 2015-part-03 — 191 problems (EN–VI)

Question 37

Let $ABC$ be a scalene acute angled triangle with $AB \lt AC \lt BC$ and circumcircle $c(O, R)$. The excircle $(c_A)$ corresponding to the vertex $A$ has center $I$ and is tangent to the sides $BC$, $AC$, $AB$ at $D$, $E$, $Z$, respectively. The line $AI$ intersects the circle $c(O, R)$ at $M$ and the circumcircle, say $(c_1)$, of the triangle $AZE$ intersects the circle $(c)$ at $K$. The circumcircle, say $(c_2)$, of the triangle $OKM$ intersects the circle $(c_1)$ at the point $N$. Prove that the lines $AN$ and $KI$ intersect at a point of the circle $(c)$.