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Bacle2
Bacle2 is offline
#3
Mar8-12, 01:45 PM
Sci Advisor
P: 1,168
Some ideas:

Have you already seen limit points? If so, try showing that both the sup and the inf (when both are finite*) , are limit points of a set. Then look for a charcterization of closed sets in terms of limit points.


*This can be extended to the infinite case too, but let's start slowly.