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| Mirrors > Home > MPE Home > Th. List > ssnnfi | Structured version Visualization version GIF version | ||
| Description: A subset of a natural number is finite. (Contributed by NM, 24-Jun-1998.) (Proof shortened by BTernaryTau, 23-Sep-2024.) |
| Ref | Expression |
|---|---|
| ssnnfi | ⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊆ 𝐴) → 𝐵 ∈ Fin) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | sspss 4102 | . 2 ⊢ (𝐵 ⊆ 𝐴 ↔ (𝐵 ⊊ 𝐴 ∨ 𝐵 = 𝐴)) | |
| 2 | pssnn 9208 | . . . . 5 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊊ 𝐴) → ∃𝑥 ∈ 𝐴 𝐵 ≈ 𝑥) | |
| 3 | elnn 7898 | . . . . . . . . 9 ⊢ ((𝑥 ∈ 𝐴 ∧ 𝐴 ∈ ω) → 𝑥 ∈ ω) | |
| 4 | 3 | expcom 413 | . . . . . . . 8 ⊢ (𝐴 ∈ ω → (𝑥 ∈ 𝐴 → 𝑥 ∈ ω)) |
| 5 | 4 | anim1d 611 | . . . . . . 7 ⊢ (𝐴 ∈ ω → ((𝑥 ∈ 𝐴 ∧ 𝐵 ≈ 𝑥) → (𝑥 ∈ ω ∧ 𝐵 ≈ 𝑥))) |
| 6 | 5 | reximdv2 3164 | . . . . . 6 ⊢ (𝐴 ∈ ω → (∃𝑥 ∈ 𝐴 𝐵 ≈ 𝑥 → ∃𝑥 ∈ ω 𝐵 ≈ 𝑥)) |
| 7 | 6 | adantr 480 | . . . . 5 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊊ 𝐴) → (∃𝑥 ∈ 𝐴 𝐵 ≈ 𝑥 → ∃𝑥 ∈ ω 𝐵 ≈ 𝑥)) |
| 8 | 2, 7 | mpd 15 | . . . 4 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊊ 𝐴) → ∃𝑥 ∈ ω 𝐵 ≈ 𝑥) |
| 9 | isfi 9016 | . . . 4 ⊢ (𝐵 ∈ Fin ↔ ∃𝑥 ∈ ω 𝐵 ≈ 𝑥) | |
| 10 | 8, 9 | sylibr 234 | . . 3 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊊ 𝐴) → 𝐵 ∈ Fin) |
| 11 | eleq1 2829 | . . . . 5 ⊢ (𝐵 = 𝐴 → (𝐵 ∈ ω ↔ 𝐴 ∈ ω)) | |
| 12 | 11 | biimparc 479 | . . . 4 ⊢ ((𝐴 ∈ ω ∧ 𝐵 = 𝐴) → 𝐵 ∈ ω) |
| 13 | nnfi 9207 | . . . 4 ⊢ (𝐵 ∈ ω → 𝐵 ∈ Fin) | |
| 14 | 12, 13 | syl 17 | . . 3 ⊢ ((𝐴 ∈ ω ∧ 𝐵 = 𝐴) → 𝐵 ∈ Fin) |
| 15 | 10, 14 | jaodan 960 | . 2 ⊢ ((𝐴 ∈ ω ∧ (𝐵 ⊊ 𝐴 ∨ 𝐵 = 𝐴)) → 𝐵 ∈ Fin) |
| 16 | 1, 15 | sylan2b 594 | 1 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊆ 𝐴) → 𝐵 ∈ Fin) |
| Colors of variables: wff setvar class |
| Syntax hints: → wi 4 ∧ wa 395 ∨ wo 848 = wceq 1540 ∈ wcel 2108 ∃wrex 3070 ⊆ wss 3951 ⊊ wpss 3952 class class class wbr 5143 ωcom 7887 ≈ cen 8982 Fincfn 8985 |
| This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1795 ax-4 1809 ax-5 1910 ax-6 1967 ax-7 2007 ax-8 2110 ax-9 2118 ax-10 2141 ax-12 2177 ax-ext 2708 ax-sep 5296 ax-nul 5306 ax-pr 5432 ax-un 7755 |
| This theorem depends on definitions: df-bi 207 df-an 396 df-or 849 df-3or 1088 df-3an 1089 df-tru 1543 df-fal 1553 df-ex 1780 df-nf 1784 df-sb 2065 df-mo 2540 df-clab 2715 df-cleq 2729 df-clel 2816 df-ne 2941 df-ral 3062 df-rex 3071 df-rab 3437 df-v 3482 df-dif 3954 df-un 3956 df-in 3958 df-ss 3968 df-pss 3971 df-nul 4334 df-if 4526 df-pw 4602 df-sn 4627 df-pr 4629 df-op 4633 df-uni 4908 df-br 5144 df-opab 5206 df-tr 5260 df-id 5578 df-eprel 5584 df-po 5592 df-so 5593 df-fr 5637 df-we 5639 df-xp 5691 df-rel 5692 df-cnv 5693 df-co 5694 df-dm 5695 df-rn 5696 df-ord 6387 df-on 6388 df-lim 6389 df-suc 6390 df-fun 6563 df-fn 6564 df-f 6565 df-f1 6566 df-fo 6567 df-f1o 6568 df-om 7888 df-en 8986 df-fin 8989 |
| This theorem is referenced by: 0finOLD 9210 ssfiALT 9214 en1eqsnOLD 9309 isfinite2 9334 wofib 9585 infpwfien 10102 fin67 10435 hashcard 14394 rexpen 16264 |
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