Problem 1601 (difficulty: 6/10)
Let \(\displaystyle f\) be continuous on the closed unit disc and holomorphic in its interior. Prove that for \(\displaystyle |z|<1\)
\(\displaystyle f(z)=\frac1{2\pi i}\int_{|z|=1}\frac{f(\xi)}{z-\xi}\dxi. \)