2.60. Pentagon $A B C D E$ is inscribed in a circle. The distances from point $E$ to the lines $A B, B C$ and $C D$ are $a, b$ and $c$ respectively. Find the distance from point $E$ to the line $A D$.
2.60. Let $K, L, M$ and $N$ be the feet of the perpendiculars dropped from point $E$ to the lines $A B, B C, C D$ and $D A$. Points $K$ and $N$ lie on the circle with diameter $A E$, so $\angle(E K, K N)=\angle(E A, A N)$. Similarly, $\angle(E L, L M)=$ $=\angle(E C, C M)=\angle(E A, A N)$, hence $\angle(E K, K N)=\angle(E L, L M)$. Similarly, $\angle(E N, N K)=\angle(E M, M L)$ and $\angle(K E, E N)=\angle(L E, E M)$. Therefore, $\triangle E K N \sim \triangle E L M$, which means $E K: E N=E L: E M$, i.e., $E N=E K \cdot E M / E L=$ $=a c / b$.