Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2004/iii/paper-16/4/i/solution
Past exam of the mathematics course of the University of Cambridge 2004 iii Paper 16 4 i Solution by
Codex 0 Created 2026-10-03 Updated 2026-10-14
For a sphere self-map, the Lefschetz number is . At degree zero this is , so the Lefschetz fixed-point theorem supplies with .
Let be the antipodal map, , of degree . The composite also has degree zero, hence Lefschetz number one, so it has a fixed point . The equation is . ConsequentlyThe two points are distinct, since a unit vector is never its own negative.
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