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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 4041 (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 3079 | . 2 ⊢ (𝐴 ⊆ 𝐵 ↔ (𝐴 ∩ 𝐵) = 𝐴) | |
2 | ssex.1 | . . . 4 ⊢ 𝐵 ∈ V | |
3 | 2 | inex2 4058 | . . 3 ⊢ (𝐴 ∩ 𝐵) ∈ V |
4 | eleq1 2200 | . . 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 1331 ∈ wcel 1480 Vcvv 2681 ∩ cin 3065 ⊆ wss 3066 |
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 698 ax-5 1423 ax-7 1424 ax-gen 1425 ax-ie1 1469 ax-ie2 1470 ax-8 1482 ax-10 1483 ax-11 1484 ax-i12 1485 ax-bndl 1486 ax-4 1487 ax-17 1506 ax-i9 1510 ax-ial 1514 ax-i5r 1515 ax-ext 2119 ax-sep 4041 |
This theorem depends on definitions: df-bi 116 df-tru 1334 df-nf 1437 df-sb 1736 df-clab 2124 df-cleq 2130 df-clel 2133 df-nfc 2268 df-v 2683 df-in 3072 df-ss 3079 |
This theorem is referenced by: ssexi 4061 ssexg 4062 inteximm 4069 funimaexglem 5201 tfrexlem 6224 elinp 7275 suplocexprlem2b 7515 negfi 10992 elcncf 12718 exmid1stab 13184 sbthom 13210 |
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