Problem 1431 (difficulty: 7/10)

Prove that if \(\displaystyle f:\R \to \R\), then the set of points of continuity is Borel, and give as small as possible of Borel-class (e.g.. \(\displaystyle G_{\delta\sigma\delta\sigma\delta\sigma\delta\sigma}\)), to which it still belongs.

Solution-->

Give me another random problem!