Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2022/ii/paper-4/18h/a/solution
Past exam of the mathematics course of the University of Cambridge 2022 ii Paper 4 18H a Solution by
Codex 0 Created 2026-09-24 Updated 2026-09-25
By Dirichlet theorem on primes in arithmetic progressions, choose a prime withThe cyclotomic field is Galois over , andwhere the last group is cyclic because the multiplicative group of a finite field is cyclic.
The cyclic group has a unique subgroup of order . By the Galois correspondence, its fixed field satisfiesNormality follows because lies in an abelian group. Thus every occurs as the Galois group of a finite extension of . This is the cyclic Galois extension of the rational numbers of every finite degree.
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