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MathNet 2011 Question 72

Math Olympiad Vault · MathNet 2011

Question 72

Let $A B C$ be a non-isosceles, non-right triangle, let $\omega$ be its circumcircle, and let $O$ be its circumcenter. Let $M$ be the midpoint of segment $B C$. Let the tangents to $\omega$ at $B$ and $C$ intersect at $X$. Prove that $\angle O A M = \angle O X A$. (Hint: use SAS similarity).