- #1
Bipolarity
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My first analysis/topology text defined the boundary of a set S as the set of all points whose neighborhoods had some point in the set S and some point outside the set S. It also defined the closure of a set S the union of S and its boundary.
Using this, we can prove that the closure of S is the smallest closed set containing S. We can also prove that the boundary of S is the intersection of the closure of S and the closure of the complement of S.
I was wondering, if we define the closure of S to be the smallest closed set containing S, and the boundary of S to be the intersection of the closure of S and the closure of the complement of S, will we have the machinery necessary to work backwards and prove the first two definitions, i.e. are the two definitions of boundary/closure equivalent?
BiP
Using this, we can prove that the closure of S is the smallest closed set containing S. We can also prove that the boundary of S is the intersection of the closure of S and the closure of the complement of S.
I was wondering, if we define the closure of S to be the smallest closed set containing S, and the boundary of S to be the intersection of the closure of S and the closure of the complement of S, will we have the machinery necessary to work backwards and prove the first two definitions, i.e. are the two definitions of boundary/closure equivalent?
BiP