Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2004/iii/paper-16/4/i/solution

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 . Consequently
The two points are distinct, since a unit vector is never its own negative.

New to topics? Read the docs here!