A First Course in Complex Analysis · Problem 8.4.12
Taylor and Laurent Series — Beck, Marchesi, Pixton & Sabalka
Mathematics — Complex Analysis
Problem
Prove Corollary 8.2.6 (Minimum-Modulus Theorem): Suppose f is holomorphic and nonconstant in a region G. Then ∣f∣ does not attain a weak relative minimum at a point a in G unless f(a)=0.