show that $S= \cup_{n \in K}(n, n+1] : K \subset Z.\ is\ \sigma-algebra.$
38946
Show that $\{\cup_{n\in K} (n, n+1]: K \subset \mathbb{Z}\}$ is a $\sigma$-algebra on $\mathbb{R}$
151295
Proving $|S \times \mathbb{N}|=|S|$ when $S$ is an infinite set
46240
Show that if $A$ and $B$ are sets, then $(A\cap B) \cup (A\cap \overline{B})=A$.
26302
Prove that $(X \cap Y) \cup Z = (X \cup Z) \cap (Y \cup Z)$
103441
Proving $(A\cup B)\cap(B\cup C)\cap(C\cup A)=(A\cap B)\cup (A\cap C)\cup (B\cap C)$?
75604
Proof that $\partial(A\times B) = ((\partial A)\times B)\cup (A\times(\partial B))$
76823
Is it the case that for all sets $A, B, C,$ and $D$, $(A \times B) \cup (C \times D) = (A \cup B) \times (C \cup D)$?
21114
$S=\{(n,{1\over n}):n\in\mathbb{N}\}$ is closed in $X$?
14713
$X=(-\infty,0]\cup\left\{{1\over n}:n\in\mathbb N\right\}$ with subspace topology Then
137707
How to prove that $(A\cup B) \cap C \subseteq A\cup (B\cap C)$
98897
Proving that the set of $\nu$ measurable sets $M\subseteq P(X)$ is an algebra
64118
Number of elements in a finite $\sigma$-algebra
104308
Proving a set is a Sigma Algebra
26215
Proof Verification: Let $D=\{ \frac{1}{n} \mid n\in\mathbb{N} \} \cup\{0\} \subset \mathbb{E}^1$. Prove that $D$ is compact.
151852
How to prove $A \subset B \iff A \cup B = B$
16048
Approximating a $\sigma$-algebra by a generating algebra
24561
$\mathbb S_n$ as semidirect product