4.I.2F

Topics in Analysis
Part II, 2005

(i) Let DCD \subset \mathbb{C} be a domain, let f:DCf: D \rightarrow \mathbb{C} be an analytic function and let z0Dz_{0} \in D. What does Taylor's theorem say about z0,fz_{0}, f and DD ?

(ii) Let KK be the square consisting of all complex numbers zz such that

1Re(z)1 and 1Im(z)1,-1 \leqslant \operatorname{Re}(z) \leqslant 1 \text { and }-1 \leqslant \operatorname{Im}(z) \leqslant 1,

and let ww be a complex number not belonging to KK. Prove that the function f(z)=f(z)= (zw)1(z-w)^{-1} can be uniformly approximated on KK by polynomials.