Solution

ID: past-exam-of-the-topology-course-of-the-university-of-oxford/2023/2/a/i/solution

The quotient set consists of the equivalence classes . Its collapsing map is the canonical projection of a quotient set
Equip this set with the quotient topology:
This is a topology because preimages preserve arbitrary unions, finite intersections, the empty set, and the whole set. The resulting topological space is the quotient space. The displayed rule immediately implies that the preimage of every open set is open, so is continuous; it is also surjective.

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