Non-Borel set/Advanced

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https://en.citizendium.org/wiki/index.php?title=Non-Borel_set/Advanced&printable=yes
An advanced level version of Non-Borel set.

The set under consideration is analytic, and complete in the class of analytic sets; therefore it is not Borel. For more details see descriptive set theory and the book by Kechris, especially Exercise (27.2) on page 209, Definition (22.9) on page 169, and Exercise (3.4)(ii) on page 14.

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