- #1
Buri
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My professor proved this result in class, but I don't understand the "simple" direction. He said that the above result is in another words proving that Cl(a) = intersection of all closed sets that contain A.
So he proved Cl(A) subset of intersection of all of the closed sets containing A. And intersection of closed sets containing A is a subset of Cl(A). However, I don't understand this last direction.
He simply says:
Cl(A) = int(A) U Bd(A); by definition.
=> Cl(A) is one of the closed sets containing A.
=> intersection of closed sets containing A is a subset of Cl(A).
That's what I just don't get. I understand that Cl(A) is closed and it contains A, but I just don't see how we can then say that the intersection of all closed sets containing A has Cl(A) in it. I know its going to be one of those I'll be intersecting all the other closed sets with, but that Cl(A) is actually INSIDE the intersection I just don't see.
I'm having a massive brain freeze so an explanation would be appreciated.
Thanks
So he proved Cl(A) subset of intersection of all of the closed sets containing A. And intersection of closed sets containing A is a subset of Cl(A). However, I don't understand this last direction.
He simply says:
Cl(A) = int(A) U Bd(A); by definition.
=> Cl(A) is one of the closed sets containing A.
=> intersection of closed sets containing A is a subset of Cl(A).
That's what I just don't get. I understand that Cl(A) is closed and it contains A, but I just don't see how we can then say that the intersection of all closed sets containing A has Cl(A) in it. I know its going to be one of those I'll be intersecting all the other closed sets with, but that Cl(A) is actually INSIDE the intersection I just don't see.
I'm having a massive brain freeze so an explanation would be appreciated.
Thanks