Problem

Source: JBMO Shortlist 2004

Tags: JBMO, geometry



Two circles $C_1$ and $C_2$ intersect in points $A$ and $B$. A circle $C$ with center in $A$ intersect $C_1$ in $M$ and $P$ and $C_2$ in $N$ and $Q$ so that $N$ and $Q$ are located on different sides wrt $MP$ and $AB> AM$. Prove that $\angle MBQ = \angle NBP$.