- #1
Buri
- 273
- 0
I'm currently reading Real Analysis by Stein and Sharkarchi and they state the following theorem:
Every open subset O of R can be written uniquely as as a countable union of disjoint open intervals.
They prove it and I understand the proof. I was just playing around with open sets, but it seems like there's no punch to it, so to speak. If I take (0,1) the 'countable union of disjoint open intervals' is the set itself and if I take the union of two open intervals then again its the set itself. I guess the open set would have to be something weird to be more interesting. Is there maybe any more interesting examples of an open set being written as a countable union of disjoint open intervals?
Thanks
Every open subset O of R can be written uniquely as as a countable union of disjoint open intervals.
They prove it and I understand the proof. I was just playing around with open sets, but it seems like there's no punch to it, so to speak. If I take (0,1) the 'countable union of disjoint open intervals' is the set itself and if I take the union of two open intervals then again its the set itself. I guess the open set would have to be something weird to be more interesting. Is there maybe any more interesting examples of an open set being written as a countable union of disjoint open intervals?
Thanks
Last edited: