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Mirrors > Home > ILE Home > Th. List > ssex | GIF version |
Description: The subset of a set is also a set. Exercise 3 of [TakeutiZaring] p. 22. This is one way to express the Axiom of Separation ax-sep 4105 (a.k.a. Subset Axiom). (Contributed by NM, 27-Apr-1994.) |
Ref | Expression |
---|---|
ssex.1 | ⊢ 𝐵 ∈ V |
Ref | Expression |
---|---|
ssex | ⊢ (𝐴 ⊆ 𝐵 → 𝐴 ∈ V) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-ss 3134 | . 2 ⊢ (𝐴 ⊆ 𝐵 ↔ (𝐴 ∩ 𝐵) = 𝐴) | |
2 | ssex.1 | . . . 4 ⊢ 𝐵 ∈ V | |
3 | 2 | inex2 4122 | . . 3 ⊢ (𝐴 ∩ 𝐵) ∈ V |
4 | eleq1 2233 | . . 3 ⊢ ((𝐴 ∩ 𝐵) = 𝐴 → ((𝐴 ∩ 𝐵) ∈ V ↔ 𝐴 ∈ V)) | |
5 | 3, 4 | mpbii 147 | . 2 ⊢ ((𝐴 ∩ 𝐵) = 𝐴 → 𝐴 ∈ V) |
6 | 1, 5 | sylbi 120 | 1 ⊢ (𝐴 ⊆ 𝐵 → 𝐴 ∈ V) |
Colors of variables: wff set class |
Syntax hints: → wi 4 = wceq 1348 ∈ wcel 2141 Vcvv 2730 ∩ cin 3120 ⊆ wss 3121 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-io 704 ax-5 1440 ax-7 1441 ax-gen 1442 ax-ie1 1486 ax-ie2 1487 ax-8 1497 ax-10 1498 ax-11 1499 ax-i12 1500 ax-bndl 1502 ax-4 1503 ax-17 1519 ax-i9 1523 ax-ial 1527 ax-i5r 1528 ax-ext 2152 ax-sep 4105 |
This theorem depends on definitions: df-bi 116 df-tru 1351 df-nf 1454 df-sb 1756 df-clab 2157 df-cleq 2163 df-clel 2166 df-nfc 2301 df-v 2732 df-in 3127 df-ss 3134 |
This theorem is referenced by: ssexi 4125 ssexg 4126 inteximm 4133 funimaexglem 5279 tfrexlem 6310 elinp 7423 suplocexprlem2b 7663 negfi 11178 ssomct 12387 ssnnctlemct 12388 nninfdc 12395 elcncf 13313 exmid1stab 13993 sbthom 14018 |
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