notesonly.in

Q: Find sup and inf of (0,1), [0,1], and {1/n: n∈ℕ}. (0,1): sup = 1 (not attained!), inf = 0 (not attained!). [0,1]: sup = 1 = max, inf = 0 = min (attained!). {1/n}: sup = 1 (n=1), inf = 0 (limit, not attained!). Max needs membership; sup doesn't!