$\overline{S} = \partial S$ $\sqcup$ $\mathring{S}$
47680
Prove that the union of the interior of a set and the boundary of the set is the closure of the set
56429
Extension of partial derivatives and the definition of $C^k(\overline{\Omega})$
67709
Stuck with proof for $\forall A\forall B(\mathcal{P}(A)\cup\mathcal{P}(B)=\mathcal{P}(A\cup B)\rightarrow A\subseteq B \vee B\subseteq A)$
19424
Showing $(M^\perp)^\perp=\overline{M}$
135751
Show that $Int(A)=X\setminus\overline{X\setminus A}$.
2667
Given $S \hookrightarrow T$ construct $U ≈ T$ disjoint from $S$ in Z set theory?
118310
How to find $\operatorname{Gal}(S/\mathbb{Q})$
115606
Proofs involving $ (A\setminus B) \cup (A \cap B)$
52596
A basis for $k(X)$ regarded as a vector space over $k$
33030
Proof that $\inf A = -\sup(-A)$
2235
Showing $\text{Aut}_\mathsf{Grp}(\mathbb{Z}/2\mathbb{Z} \times \mathbb{Z}/2\mathbb{Z}) \cong S_3$
35115
Questions on how to prove that a set of connectives is NOT functionally complete
149801
prove that $TS = ST$
151295
Proving $|S \times \mathbb{N}|=|S|$ when $S$ is an infinite set
30231
The boundary of union is the union of boundaries when the sets have disjoint closures
66824
Two definitions of $\limsup$
78804
Proving that $\mathscr L=\{0^n \big|\text{n is the square of a natural number }\}$ is non regular using the pumping lemma