How to give proof of union of subsets
56399
Proof for $A \cup B = B$ if and only if $A \subset B$
23225
Union of connected subsets is connected if intersection is nonempty
134120
Prove statement with a counter-example: For all sets S, T and V, V ∪ (S ∩ T) = (V ∪ S) ∩ T is false
87830
Relating the union of the power set of a set to the set itself
150738
Proof of $(A - B) - C = A - (B \cup C)$
80916
How to prove that if $A\subseteq A\times A$, then $A=\varnothing$?
91180
Show $R \setminus S$ is a union of prime ideals
118239
If $A, B, C$ are sets prove that $(A\setminus B)\setminus C\subseteq A\setminus(B\setminus C)$
51617
What is the proof that the total number of subsets of a set is $2^n$?
30231
The boundary of union is the union of boundaries when the sets have disjoint closures
105886
A question on the proof of 14 distinct sets can be formed by complementation and closure
109682
Proposed proof of: If $A \subset B \subset \bar{A}$ and $A$ is connected, then $B$ is connected
89127
How do I prove if a set of operations is complete?
123090
How to show that disjoint closed sets have disjoint open supersets?
67709
Stuck with proof for $\forall A\forall B(\mathcal{P}(A)\cup\mathcal{P}(B)=\mathcal{P}(A\cup B)\rightarrow A\subseteq B \vee B\subseteq A)$
46240
Show that if $A$ and $B$ are sets, then $(A\cap B) \cup (A\cap \overline{B})=A$.
41192
Neatest proof that set of finite subsets is countable?