In: Advanced Math
This question revisits 2.4.7 from Abbott. Remind yourself of the definition of lim sup. Let (an) be a bounded sequence. Let S = {s ∈ R : ∃ a subsequence (ank ) converging to s}. This is called the set of subsequential limits. Bolzano-Weierstrass theorem implies there is at least one convergent subsequence, so S cannot equal ∅. Show S is bounded and lim sup an=sup(S).