Английская Википедия:Coanalytic set
Материал из Онлайн справочника
In the mathematical discipline of descriptive set theory, a coanalytic set is a set (typically a set of real numbers or more generally a subset of a Polish space) that is the complement of an analytic set (Kechris 1994:87). Coanalytic sets are also referred to as <math>\boldsymbol{\Pi}^1_1</math> sets (see projective hierarchy).
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