# Thread: Closed and Unbounded set?

1. ## Closed and Unbounded set?

Open and bounded sets seem to be abound (no pun intended), but I cannot think of any examples of closed and unbounded set, except for the trivial R and null sets.

Do you know of any such sets?

2. The integers

3. Originally Posted by amoeba
Open and bounded sets seem to be abound (no pun intended), but I cannot think of any examples of closed and unbounded set, except for the trivial R and null sets.

Do you know of any such sets?

Any interval of the form [a,oo) or (-oo, a] is closed and unbounded.

Tonio

4. the complement of any bounded open set is actually also closed and unbounded. Not all are gotten in this way though, as my first example demonstrates

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# Closed and unbounded set

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