List questions from elementary-set-theory

Published on 08 Apr 2026 - 8:59

60

Views

Let $f : X \to Y$ be surjective. Show that there exists an injection $h : Y \to X$ such that $f \circ h = Id_Y$

Published on 12 Apr 2026 - 18:09

138

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Is the set of the specific sequences of 0's and 1's countable?

Published on 18 Mar 2018 - 11:57

243

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Frontier points counter example

Published on 11 Apr 2026 - 23:27

3k

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Prove that P (A ∪ B) = P (A) ∪ P(B) is true iff B ⊆ A or A ⊆ B.

Published on 18 Mar 2018 - 16:20

43

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Sets of students, unions, complements, intersections

Published on 25 Mar 2026 - 7:41

439

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My Proof for subset of a finite set is finite

Published on 29 Mar 2026 - 9:11

4.5k

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Does there exist a set containing infinite elements, whose elements themselves are sets containing infinite elements?

Published on 18 Mar 2018 - 22:19

45

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Expressing the union and intersection of sets

Published on 19 Mar 2018 - 1:09

2.3k

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Finding the number of Partitions in a set into two subsets

Published on 11 Apr 2026 - 21:46

89

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Commutativity of $\bigcup$, $\sum$, $\bigvee$

Published on 12 Apr 2026 - 11:10

1k

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Notation for function spaces

Published on 09 Apr 2026 - 11:09

86

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Set Existence Within ZFC

Published on 19 Mar 2018 - 17:59

456

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Cardinality of a set that contains duplicate sets

Published on 25 Mar 2026 - 12:53

420

Views

Prove that $\bigcap_{x\in\mathbb R}[3 - x^2, 5 + x^2]$ is contained in $[3,5]$.

Published on 29 Mar 2026 - 3:27

List Question

Help Interpreting a Problem Concerning the Union of Connected Sets

Let $f : X \to Y$ be surjective. Show that there exists an injection $h : Y \to X$ such that $f \circ h = Id_Y$

Is the set of the specific sequences of 0's and 1's countable?

Frontier points counter example

Prove that P (A ∪ B) = P (A) ∪ P(B) is true iff B ⊆ A or A ⊆ B.

Sets of students, unions, complements, intersections

My Proof for subset of a finite set is finite

Does there exist a set containing infinite elements, whose elements themselves are sets containing infinite elements?

Expressing the union and intersection of sets

Finding the number of Partitions in a set into two subsets

Commutativity of $\bigcup$, $\sum$, $\bigvee$

Notation for function spaces

Set Existence Within ZFC

Cardinality of a set that contains duplicate sets

Prove that $\bigcap_{x\in\mathbb R}[3 - x^2, 5 + x^2]$ is contained in $[3,5]$.

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