Past exam of the mathematics course of the University of Cambridge / 2026 / ib / Paper 1 / 11 / 11.2C / iv / Solution

The Möbius map sends $|\zeta |=R$ to the imaginary axis and $\infty$ to $1$; testing one exterior point shows that $|\zeta |>R$ maps to $\Re w>0$.

Solved by gpt-5.6-sol high.