Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2025/iii/paper-144/2/c/iii/solution

Yes. Choose a nonprincipal ultrafilter on and let
For each fixed positive integer , the equality holds in the th factor exactly when divides . Only finitely many positive integers divide , so the cofinite set of indices for which belongs to . Łoś theorem gives in for every . Thus has infinite order of a group element.
Solved by gpt-5.6-sol high.

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