Question

Proving the union of countably many countable sets is countable without axiom of choice.

score 225 · Answer 1 · 2026-04-16 05:51:46

225

Views

Proving the union of countably many countable sets is countable without axiom of choice.

Published on 16 Apr 2026 - 5:51

score 353 · Answer 2 · 2026-04-11 19:13:40

353

Views

Prove that $\omega$ is not successor ordinal

Published on 11 Apr 2026 - 19:13

score 102 · Answer 3 · 2026-04-14 10:39:21

102

Views

Possible combinations of permutations between N variable-size sets without repetition

Published on 14 Apr 2026 - 10:39

score 248 · Answer 4 · 2026-04-17 15:12:09

248

Views

set theory similarity between sets : Are $\{0,1\}×\mathbb R$ and $\mathbb N×\mathbb R$ similar?

Published on 17 Apr 2026 - 15:12

score 212 · Answer 5 · 2026-04-14 12:21:08

212

Views

what does $S \times T $ (read as $S$ cross $T$) or $S \times S$ (read as $S$ cross $S$) in set theory?

Published on 14 Apr 2026 - 12:21

score 2k · Answer 6 · 2026-04-16 03:00:03

2k

Views

Which one of the following statements is correct regarding the elements and subsets of the set

Published on 16 Apr 2026 - 3:00

score 45 · Answer 7 · 2026-04-16 10:39:47

45

Views

A subset is a set

Published on 16 Apr 2026 - 10:39

score 68 · Answer 8 · 2026-04-17 03:55:29

68

Views

Show that $f^{-1}(Y\setminus B_{1})=X\setminus f^{-1}(B_{1})$.

Published on 17 Apr 2026 - 3:55

score 136 · Answer 9 · 2026-04-12 04:02:43

136

Views

How to prove that $N\setminus A$ is finite?

Published on 12 Apr 2026 - 4:02

score 59 · Answer 10 · 2026-04-10 14:27:28

59

Views

Function notation issue

Published on 10 Apr 2026 - 14:27

score 72 · Answer 11 · 2026-04-11 15:51:30

72

Views

The Field of a Relation $R$

Published on 11 Apr 2026 - 15:51

score 37 · Answer 12 · 2026-04-08 02:28:58

37

Views

Can I prove this set relation using associativity?

Published on 08 Apr 2026 - 2:28

score 238 · Answer 13 · 2026-04-14 22:27:40

238

Views

Show that infinite Cartesian product is uncountable

Published on 14 Apr 2026 - 22:27

score 173 · Answer 14 · 2026-04-10 15:16:14

173

Views

How do I use prove this function is bijective?

Published on 10 Apr 2026 - 15:16

score 61 · Answer 15 · 2026-04-13 23:03:37

61

Views

How to write that the sum of two numbers is an element of set {1, 2, .., 8} in set theory?

Published on 13 Apr 2026 - 23:03

List Question

Proving the union of countably many countable sets is countable without axiom of choice.

Prove that $\omega$ is not successor ordinal

Possible combinations of permutations between N variable-size sets without repetition

set theory similarity between sets : Are $\{0,1\}×\mathbb R$ and $\mathbb N×\mathbb R$ similar?

what does $S \times T $ (read as $S$ cross $T$) or $S \times S$ (read as $S$ cross $S$) in set theory?

Which one of the following statements is correct regarding the elements and subsets of the set

A subset is a set

Show that $f^{-1}(Y\setminus B_{1})=X\setminus f^{-1}(B_{1})$.

How to prove that $N\setminus A$ is finite?

Function notation issue

The Field of a Relation $R$

Can I prove this set relation using associativity?

Show that infinite Cartesian product is uncountable

How do I use prove this function is bijective?

How to write that the sum of two numbers is an element of set {1, 2, .., 8} in set theory?

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