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MathNet 2011 Question 92

Math Olympiad Vault · MathNet 2011

Question 92

The circles $\Gamma_1$ and $\Gamma_2$ meet at $D$ and $P$. Their common tangent closest to $D$ touches $\Gamma_1$ at $A$ and $\Gamma_2$ at $B$. The line $AD$ meets $\Gamma_2$ again at $C$. Let $M$ be the midpoint of $BC$.
Prove that $\angle DPM=\angle BDC$.

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