3.I.2 F3 . \mathrm{I} . 2 \mathrm{~F}

Topics in Analysis
Part II, 2007

State a version of Runge's theorem and use it to prove the following theorem:

Let D={zC:z<1}D=\{z \in \mathbb{C}:|z|<1\} and define f:DCf: D \rightarrow \mathbb{C} by the condition

f(reiθ)=r3/2e3iθ/2f\left(r e^{i \theta}\right)=r^{3 / 2} e^{3 i \theta / 2}

for all 0r<10 \leqslant r<1 and all 0θ<2π0 \leqslant \theta<2 \pi. (We take r1/2r^{1 / 2} to be the positive square root.) Then there exists a sequence of analytic functions fn:DCf_{n}: D \rightarrow \mathbb{C} such that fn(z)f(z)f_{n}(z) \rightarrow f(z) for each zDz \in D as nn \rightarrow \infty.