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Mirrors > Home > ILE Home > Th. List > ssdifss | GIF version |
Description: Preservation of a subclass relationship by class difference. (Contributed by NM, 15-Feb-2007.) |
Ref | Expression |
---|---|
ssdifss | ⊢ (𝐴 ⊆ 𝐵 → (𝐴 ∖ 𝐶) ⊆ 𝐵) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | difss 3149 | . 2 ⊢ (𝐴 ∖ 𝐶) ⊆ 𝐴 | |
2 | sstr 3055 | . 2 ⊢ (((𝐴 ∖ 𝐶) ⊆ 𝐴 ∧ 𝐴 ⊆ 𝐵) → (𝐴 ∖ 𝐶) ⊆ 𝐵) | |
3 | 1, 2 | mpan 418 | 1 ⊢ (𝐴 ⊆ 𝐵 → (𝐴 ∖ 𝐶) ⊆ 𝐵) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∖ cdif 3018 ⊆ wss 3021 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in1 584 ax-in2 585 ax-io 671 ax-5 1391 ax-7 1392 ax-gen 1393 ax-ie1 1437 ax-ie2 1438 ax-8 1450 ax-10 1451 ax-11 1452 ax-i12 1453 ax-bndl 1454 ax-4 1455 ax-17 1474 ax-i9 1478 ax-ial 1482 ax-i5r 1483 ax-ext 2082 |
This theorem depends on definitions: df-bi 116 df-tru 1302 df-nf 1405 df-sb 1704 df-clab 2087 df-cleq 2093 df-clel 2096 df-nfc 2229 df-v 2643 df-dif 3023 df-in 3027 df-ss 3034 |
This theorem is referenced by: ssdifssd 3161 |
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