A D11: Set $F \subseteq X$ is

**closed**in $T$ if and only if \begin{equation} X \setminus F \in \mathcal{T} \end{equation}

Definition D98

Closed set

Formulation 0

Let $T = (X, \mathcal{T})$ be a D1106: Topological space.

A D11: Set $F \subseteq X$ is**closed** in $T$ if and only if
\begin{equation}
X \setminus F \in \mathcal{T}
\end{equation}

A D11: Set $F \subseteq X$ is

Children

▶ | Clopen set |

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