4.I.4E

Complex Analysis | Part IB, 2008

Suppose that ff and gg are two functions which are analytic on the whole complex plane C\mathbb{C}. Suppose that there is a sequence of distinct points z1,z2,z_{1}, z_{2}, \ldots with zi1\left|z_{i}\right| \leqslant 1 such that f(zi)=g(zi)f\left(z_{i}\right)=g\left(z_{i}\right). Show that f(z)=g(z)f(z)=g(z) for all zCz \in \mathbb{C}. [You may assume any results on Taylor expansions you need, provided they are clearly stated.]

What happens if the assumption that zi1\left|z_{i}\right| \leqslant 1 is dropped?

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