Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2026/ii/paper-2/21h/solution

Homotopy equivalence means maps , with and . Radial retraction of and contraction of give . Coordinates identify , so . The map to unordered roots is a two-sheeted covering. Its induced subgroup is inside , while exchanging roots is a generator; hence .

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