Question

Let X be a topological space with topology T = P(X). Prove that X is finite if and only if X is compact. (Note: You may assume you proved that if ∣X∣ = n, then ∣P(X)∣ = 2 n in homework 2, problem 2 and simply reference this. Hint: Ô⇒ follows from the fact that if X is finite, T is also finite (why?). Therefore every open cover is already finite. For the reverse direction, consider the contrapositive. Suppose X is infinite. Construct an infinite open cover A for which every element belongs to exactly one set on A . Then there cannot exist a finite subcover since deleting any set leaves at least one point uncovered.

Answer 1