"Let f be a real-valued function defined for all real numbers. Prove that the set of points at which f is continuous is a [tex]G_\delta[/tex]."(adsbygoogle = window.adsbygoogle || []).push({});

(a set is a [tex]G_\delta[/tex] if it is the intersection of a countable collection of open sets)

I think it's obvious that I should use the topological/open-set definition of continuous, and then intersect a bunch of open sets but I'm not sure how to write it down. (if that makes any sense)

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# Homework Help: Another problem about sets

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