Solution

ID: past-exam-of-the-metric-spaces-and-complex-analysis-course-of-the-university-of-oxford/2023/2/a/ii/solution

Let be any sequence in the compact metric space . There must be an such that every open ball about contains for infinitely many indices . Otherwise, for each choose a ball containing only finitely many terms, counted by indices. These balls are an open cover. A finite subcover would imply that only finitely many indices occur anywhere in , a contradiction.
Now choose successively with ; infinitely many available indices make this possible. Then , so is a convergent subsequence. Thus
The proof counts indices rather than distinct points, so it also handles a value repeated infinitely often.

New to topics? Read the docs here!