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APMO 2014 - Asian Pacific Mathematics Olympiad Question 5

APMO · APMO 2014 - Asian Pacific Mathematics Olympiad

Question 5

Circles $\omega$ and $\Omega$ meet at $A,B$. Let $M$ be the midpoint of the arc $AB$ of $\omega$ lying inside $\Omega$. A chord $MP$ of $\omega$ intersects $\Omega$ at $Q$ inside $\omega$. Let $\ell_P$ be the tangent to $\omega$ at $P$ and $\ell_Q$ the tangent to $\Omega$ at $Q$. Prove that the circumcircle of the triangle formed by $\ell_P,\ell_Q,AB$ is tangent to $\Omega$.

Proposed by Ilya Bogdanov, Russia, and Medeubek Kungozhin, Kazakhstan.

Newly drawn configuration: Question illustration