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Mirrors > Home > MPE Home > Th. List > infn0 | Structured version Visualization version GIF version |
Description: An infinite set is not empty. For a shorter proof using ax-un 7754, see infn0ALT 9339. (Contributed by NM, 23-Oct-2004.) Avoid ax-un 7754. (Revised by BTernaryTau, 8-Jan-2025.) |
Ref | Expression |
---|---|
infn0 | ⊢ (ω ≼ 𝐴 → 𝐴 ≠ ∅) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | brdomi 8998 | . 2 ⊢ (ω ≼ 𝐴 → ∃𝑓 𝑓:ω–1-1→𝐴) | |
2 | peano1 7911 | . . . . . 6 ⊢ ∅ ∈ ω | |
3 | f1f1orn 6860 | . . . . . . . . 9 ⊢ (𝑓:ω–1-1→𝐴 → 𝑓:ω–1-1-onto→ran 𝑓) | |
4 | 3 | adantr 480 | . . . . . . . 8 ⊢ ((𝑓:ω–1-1→𝐴 ∧ 𝐴 = ∅) → 𝑓:ω–1-1-onto→ran 𝑓) |
5 | f1f 6805 | . . . . . . . . . . 11 ⊢ (𝑓:ω–1-1→𝐴 → 𝑓:ω⟶𝐴) | |
6 | 5 | frnd 6745 | . . . . . . . . . 10 ⊢ (𝑓:ω–1-1→𝐴 → ran 𝑓 ⊆ 𝐴) |
7 | sseq0 4409 | . . . . . . . . . 10 ⊢ ((ran 𝑓 ⊆ 𝐴 ∧ 𝐴 = ∅) → ran 𝑓 = ∅) | |
8 | 6, 7 | sylan 580 | . . . . . . . . 9 ⊢ ((𝑓:ω–1-1→𝐴 ∧ 𝐴 = ∅) → ran 𝑓 = ∅) |
9 | 8 | f1oeq3d 6846 | . . . . . . . 8 ⊢ ((𝑓:ω–1-1→𝐴 ∧ 𝐴 = ∅) → (𝑓:ω–1-1-onto→ran 𝑓 ↔ 𝑓:ω–1-1-onto→∅)) |
10 | 4, 9 | mpbid 232 | . . . . . . 7 ⊢ ((𝑓:ω–1-1→𝐴 ∧ 𝐴 = ∅) → 𝑓:ω–1-1-onto→∅) |
11 | f1ocnv 6861 | . . . . . . 7 ⊢ (𝑓:ω–1-1-onto→∅ → ◡𝑓:∅–1-1-onto→ω) | |
12 | noel 4344 | . . . . . . . 8 ⊢ ¬ ∅ ∈ ∅ | |
13 | f1o00 6884 | . . . . . . . . . 10 ⊢ (◡𝑓:∅–1-1-onto→ω ↔ (◡𝑓 = ∅ ∧ ω = ∅)) | |
14 | 13 | simprbi 496 | . . . . . . . . 9 ⊢ (◡𝑓:∅–1-1-onto→ω → ω = ∅) |
15 | 14 | eleq2d 2825 | . . . . . . . 8 ⊢ (◡𝑓:∅–1-1-onto→ω → (∅ ∈ ω ↔ ∅ ∈ ∅)) |
16 | 12, 15 | mtbiri 327 | . . . . . . 7 ⊢ (◡𝑓:∅–1-1-onto→ω → ¬ ∅ ∈ ω) |
17 | 10, 11, 16 | 3syl 18 | . . . . . 6 ⊢ ((𝑓:ω–1-1→𝐴 ∧ 𝐴 = ∅) → ¬ ∅ ∈ ω) |
18 | 2, 17 | mt2 200 | . . . . 5 ⊢ ¬ (𝑓:ω–1-1→𝐴 ∧ 𝐴 = ∅) |
19 | 18 | imnani 400 | . . . 4 ⊢ (𝑓:ω–1-1→𝐴 → ¬ 𝐴 = ∅) |
20 | 19 | neqned 2945 | . . 3 ⊢ (𝑓:ω–1-1→𝐴 → 𝐴 ≠ ∅) |
21 | 20 | exlimiv 1928 | . 2 ⊢ (∃𝑓 𝑓:ω–1-1→𝐴 → 𝐴 ≠ ∅) |
22 | 1, 21 | syl 17 | 1 ⊢ (ω ≼ 𝐴 → 𝐴 ≠ ∅) |
Colors of variables: wff setvar class |
Syntax hints: ¬ wn 3 → wi 4 ∧ wa 395 = wceq 1537 ∃wex 1776 ∈ wcel 2106 ≠ wne 2938 ⊆ wss 3963 ∅c0 4339 class class class wbr 5148 ◡ccnv 5688 ran crn 5690 –1-1→wf1 6560 –1-1-onto→wf1o 6562 ωcom 7887 ≼ cdom 8982 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1792 ax-4 1806 ax-5 1908 ax-6 1965 ax-7 2005 ax-8 2108 ax-9 2116 ax-12 2175 ax-ext 2706 ax-sep 5302 ax-nul 5312 ax-pr 5438 |
This theorem depends on definitions: df-bi 207 df-an 396 df-or 848 df-3or 1087 df-3an 1088 df-tru 1540 df-fal 1550 df-ex 1777 df-sb 2063 df-mo 2538 df-clab 2713 df-cleq 2727 df-clel 2814 df-ne 2939 df-ral 3060 df-rex 3069 df-rab 3434 df-v 3480 df-dif 3966 df-un 3968 df-in 3970 df-ss 3980 df-pss 3983 df-nul 4340 df-if 4532 df-pw 4607 df-sn 4632 df-pr 4634 df-op 4638 df-uni 4913 df-br 5149 df-opab 5211 df-tr 5266 df-id 5583 df-eprel 5589 df-po 5597 df-so 5598 df-fr 5641 df-we 5643 df-xp 5695 df-rel 5696 df-cnv 5697 df-co 5698 df-dm 5699 df-rn 5700 df-ord 6389 df-on 6390 df-lim 6391 df-fun 6565 df-fn 6566 df-f 6567 df-f1 6568 df-fo 6569 df-f1o 6570 df-om 7888 df-dom 8986 |
This theorem is referenced by: infpwfien 10100 infxp 10252 infpss 10254 alephmul 10616 csdfil 23918 |
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