Question 113
Points $K$ and $N$ are marked on the sides $AB$ and $AC$ of the triangle $ABC$, respectively, such that $KB = KN$. The bisector of the angle $ACB$ meets the circumcircle of $ABC$ at points $C$ and $R$. The perpendicular from $R$ on $AB$ intersects the segment $BN$ at $D$.
Prove that the points $A$, $K$, $D$, $N$ are concyclic.
(S. Mazanik)
Prove that the points $A$, $K$, $D$, $N$ are concyclic.
(S. Mazanik)