Question 137
Let $ABCD$ be a convex quadrilateral and internal bisectors of angles $B$ and $D$ meet at $I$. Fix points $M$ and $N$ on the segments $BI$ and $DI$ respectively such that $\angle MAN = \frac{1}{2} \cdot \angle A$.
Find the condition about the $ABCD$ quadrilateral such that $\angle MCN = \frac{1}{2} \cdot \angle C$?
(Russia)
Find the condition about the $ABCD$ quadrilateral such that $\angle MCN = \frac{1}{2} \cdot \angle C$?
(Russia)