Question 107
On the circle $k$ with the center at the point $O$, we select the points $A$ and $B$ so that the selected points are not the intersection of the diameter. On the circle $OAB$ circle, we select the point $C$, which does not coincide with either $A$ or $B$. The line $AC$ intersects the circle $k$ at the points $A$ and $D$. Prove that the triangle $DCB$ is isosceles.