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Mirrors > Home > ILE Home > Th. List > ax9vsep | GIF version |
Description: Derive a weakened version of ax-9 1479, where 𝑥 and 𝑦 must be distinct, from Separation ax-sep 3986 and Extensionality ax-ext 2082. In intuitionistic logic a9evsep 3990 is stronger and also holds. (Contributed by NM, 12-Nov-2013.) (Proof modification is discouraged.) (New usage is discouraged.) |
Ref | Expression |
---|---|
ax9vsep | ⊢ ¬ ∀𝑥 ¬ 𝑥 = 𝑦 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | a9evsep 3990 | . 2 ⊢ ∃𝑥 𝑥 = 𝑦 | |
2 | exalim 1446 | . 2 ⊢ (∃𝑥 𝑥 = 𝑦 → ¬ ∀𝑥 ¬ 𝑥 = 𝑦) | |
3 | 1, 2 | ax-mp 7 | 1 ⊢ ¬ ∀𝑥 ¬ 𝑥 = 𝑦 |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 ∀wal 1297 = wceq 1299 ∃wex 1436 |
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-5 1391 ax-gen 1393 ax-ie1 1437 ax-ie2 1438 ax-4 1455 ax-ial 1482 ax-ext 2082 ax-sep 3986 |
This theorem depends on definitions: df-bi 116 df-tru 1302 df-fal 1305 |
This theorem is referenced by: (None) |
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