Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2025/ib/paper-3/13e/solution

Cauchy's formula gives for an entire function bounded by on every radius- circle. If is globally bounded, letting gives , proving Liouville's theorem.
Set . Its limit at zero makes the singularity removable, so
Consequently and .
The argument principle on a large circle gives number of zeros minus poles equal to the winding number of , which is zero because . Thus . The function
has removable singularities everywhere and tends to one at infinity. Liouville gives , hence

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