I understand that showing [itex]\mathbb Q[/itex] is not a [itex]G_\delta[/itex] set is quite a non-trivial exercise, involving (among other things) an invocation of the Baire category theorem. Do any of you guys know it, or know where I can find it online? I'd really appreciate it. Thanks!(adsbygoogle = window.adsbygoogle || []).push({});

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# Proof that the rationals are not a G_\delta set.

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