Definition:Perfect Set/Definition 1

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A perfect set of a topological space $T = \left({S, \tau}\right)$ is a subset $H \subseteq S$ such that:

$H = H'$

where $H'$ is the derived set of $H$.

That is, where:

every point of $H$ is a limit point of $H$


every limit point of $H$ is a point of $H$.

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