Science Fair Project Encyclopedia
F-sigma set
In mathematics, an Fσ set (said F-sigma set) is a countable union of closed sets. In metrizable spaces, every open set is an Fσ set.
The complement of a Fσ set is a Gδ set. In a metrizable space, any closed set is a Gδ set.
The union of countably many Fσ sets is an Fσ set, and the intersection of finitely many Fσ sets is an Fσ set.
10-26-2009 08:16:03
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The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details