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Mirrors > Home > ILE Home > Th. List > nfss | GIF version |
Description: If 𝑥 is not free in 𝐴 and 𝐵, it is not free in 𝐴 ⊆ 𝐵. (Contributed by NM, 27-Dec-1996.) |
Ref | Expression |
---|---|
dfss2f.1 | ⊢ Ⅎ𝑥𝐴 |
dfss2f.2 | ⊢ Ⅎ𝑥𝐵 |
Ref | Expression |
---|---|
nfss | ⊢ Ⅎ𝑥 𝐴 ⊆ 𝐵 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | dfss2f.1 | . . 3 ⊢ Ⅎ𝑥𝐴 | |
2 | dfss2f.2 | . . 3 ⊢ Ⅎ𝑥𝐵 | |
3 | 1, 2 | dfss3f 3129 | . 2 ⊢ (𝐴 ⊆ 𝐵 ↔ ∀𝑥 ∈ 𝐴 𝑥 ∈ 𝐵) |
4 | nfra1 2495 | . 2 ⊢ Ⅎ𝑥∀𝑥 ∈ 𝐴 𝑥 ∈ 𝐵 | |
5 | 3, 4 | nfxfr 1461 | 1 ⊢ Ⅎ𝑥 𝐴 ⊆ 𝐵 |
Colors of variables: wff set class |
Syntax hints: Ⅎwnf 1447 ∈ wcel 2135 Ⅎwnfc 2293 ∀wral 2442 ⊆ wss 3111 |
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 699 ax-5 1434 ax-7 1435 ax-gen 1436 ax-ie1 1480 ax-ie2 1481 ax-8 1491 ax-10 1492 ax-11 1493 ax-i12 1494 ax-bndl 1496 ax-4 1497 ax-17 1513 ax-i9 1517 ax-ial 1521 ax-i5r 1522 ax-ext 2146 |
This theorem depends on definitions: df-bi 116 df-nf 1448 df-sb 1750 df-clab 2151 df-cleq 2157 df-clel 2160 df-nfc 2295 df-ral 2447 df-in 3117 df-ss 3124 |
This theorem is referenced by: ssrexf 3199 nfpw 3566 ssiun2s 3904 triun 4087 ssopab2b 4248 nffrfor 4320 tfis 4554 nfrel 4683 nffun 5205 nff 5328 fvmptssdm 5564 ssoprab2b 5890 nfsum1 11283 nfsum 11284 nfcprod1 11481 nfcprod 11482 |
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