Talk:Gδ set
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[edit] quesstion
Would it perhaps make more sense to combine the Gδ and Fσ articles into one article on Borel sets? --68.102.149.76 20:40, 16 September 2006 (UTC)
[edit] Continuous function
The fact that the set of points where aq function f is continuous is a Gδ set follows immediately from the fact that continuity at a point p can be defined by a 
formula - the formula states that for every natural number E > 0 there exists a natural number N > 0 such that whenever 0 < | x − p | < 1 / N, we have | f(x) − f(p) | < 1 / E. If you fix a value of E, the set of x for which there is a corresponding N is an open set, and the universal quantifier on the E corresponds to the intersection of these sets. — Carl (CBM · talk) 12:15, 16 March 2008 (UTC)
