Question 187
In a quadrilateral $ABCD$ sides $AB$ and $CD$ are not parallel. The midpoints of $AD$ and $BC$ are denoted by $M$ and $N$, respectively. The line $MN$ intersects the diagonals $AC$ and $BD$ at points $K$ and $L$, respectively. Prove that the circumcircles of triangles $AKM$ and $BNL$ intersect on the line $AB$.