Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2025/iii/paper-114/1/c/solution

The point on the quotient equator has two preimages. Small discs around them become four half-discs glued along their common diameter, so a neighborhood of is the cone on a graph with two vertices joined by four edges. The Excision theorem and the local homology from a link identify
where is this four-edge graph. It is connected and has first Betti number . Hence
Solved by gpt-5.6-sol high.

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