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Mirrors > Home > ILE Home > Th. List > ddifss | GIF version |
Description: Double complement under universal class. In classical logic (or given an additional hypothesis, as in ddifnel 3103), this is equality rather than subset. (Contributed by Jim Kingdon, 24-Jul-2018.) |
Ref | Expression |
---|---|
ddifss | ⊢ 𝐴 ⊆ (V ∖ (V ∖ 𝐴)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ssv 3019 | . 2 ⊢ 𝐴 ⊆ V | |
2 | ssddif 3198 | . 2 ⊢ (𝐴 ⊆ V ↔ 𝐴 ⊆ (V ∖ (V ∖ 𝐴))) | |
3 | 1, 2 | mpbi 143 | 1 ⊢ 𝐴 ⊆ (V ∖ (V ∖ 𝐴)) |
Colors of variables: wff set class |
Syntax hints: Vcvv 2601 ∖ cdif 2970 ⊆ wss 2973 |
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-in1 576 ax-in2 577 ax-io 662 ax-5 1376 ax-7 1377 ax-gen 1378 ax-ie1 1422 ax-ie2 1423 ax-8 1435 ax-10 1436 ax-11 1437 ax-i12 1438 ax-bndl 1439 ax-4 1440 ax-17 1459 ax-i9 1463 ax-ial 1467 ax-i5r 1468 ax-ext 2063 |
This theorem depends on definitions: df-bi 115 df-tru 1287 df-nf 1390 df-sb 1686 df-clab 2068 df-cleq 2074 df-clel 2077 df-nfc 2208 df-v 2603 df-dif 2975 df-in 2979 df-ss 2986 |
This theorem is referenced by: ssindif0im 3303 difdifdirss 3327 |
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