Question 152
Let $c(O, R)$ be a circle with diameter $AB$ and $C$ a point on it different than $A$ and $B$ such that $\angle AOC \gt 90^\circ$. On the radius $OC$ we consider the point $K$ and the circle ($c_1$) with center $K$ and radius $KC = R_1$. We draw the tangents $AD$ and $AE$ from $A$ to the circle ($c_1$). Prove that the straight lines $AC$, $BK$ and $DE$ are concurrent.