EDB — 0HJ

[0HJ]Given \(E⊆ X\), we distinguish the points \(x∈ X\) in three distinct sets that are a partition of \(X\).

• For every neighborhood \(U\) of \(x\), \(U⧵\{ x\} \) intersects \(E\). These are the accumulation points of \(E\).

• \(x∈ E\) and there is a neighborhood \(U\) of \(x\) such that \(U∩ E =\{ x\} \). These are the isolated points in \(E\).

• Now describe the third set of points