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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 3922 (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 2997 | . 2 ⊢ (𝐴 ⊆ 𝐵 ↔ (𝐴 ∩ 𝐵) = 𝐴) | |
2 | ssex.1 | . . . 4 ⊢ 𝐵 ∈ V | |
3 | 2 | inex2 3939 | . . 3 ⊢ (𝐴 ∩ 𝐵) ∈ V |
4 | eleq1 2145 | . . 3 ⊢ ((𝐴 ∩ 𝐵) = 𝐴 → ((𝐴 ∩ 𝐵) ∈ V ↔ 𝐴 ∈ V)) | |
5 | 3, 4 | mpbii 146 | . 2 ⊢ ((𝐴 ∩ 𝐵) = 𝐴 → 𝐴 ∈ V) |
6 | 1, 5 | sylbi 119 | 1 ⊢ (𝐴 ⊆ 𝐵 → 𝐴 ∈ V) |
Colors of variables: wff set class |
Syntax hints: → wi 4 = wceq 1285 ∈ wcel 1434 Vcvv 2612 ∩ cin 2983 ⊆ wss 2984 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 104 ax-ia2 105 ax-ia3 106 ax-io 663 ax-5 1377 ax-7 1378 ax-gen 1379 ax-ie1 1423 ax-ie2 1424 ax-8 1436 ax-10 1437 ax-11 1438 ax-i12 1439 ax-bndl 1440 ax-4 1441 ax-17 1460 ax-i9 1464 ax-ial 1468 ax-i5r 1469 ax-ext 2065 ax-sep 3922 |
This theorem depends on definitions: df-bi 115 df-tru 1288 df-nf 1391 df-sb 1688 df-clab 2070 df-cleq 2076 df-clel 2079 df-nfc 2212 df-v 2614 df-in 2990 df-ss 2997 |
This theorem is referenced by: ssexi 3942 ssexg 3943 inteximm 3950 funimaexglem 5049 tfrexlem 6030 elinp 6935 negfi 10483 |
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