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Mirrors > Home > MPE Home > Th. List > phplem1 | Structured version Visualization version GIF version |
Description: Lemma for Pigeonhole Principle. A natural number is equinumerous to its successor minus any element of the successor. (Contributed by NM, 26-May-1998.) Avoid ax-pow 5288. (Revised by BTernaryTau, 23-Sep-2024.) |
Ref | Expression |
---|---|
phplem1 | ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ suc 𝐴) → 𝐴 ≈ (suc 𝐴 ∖ {𝐵})) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | simpl 483 | . . 3 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ suc 𝐴) → 𝐴 ∈ ω) | |
2 | peano2 7729 | . . . . 5 ⊢ (𝐴 ∈ ω → suc 𝐴 ∈ ω) | |
3 | enrefnn 8826 | . . . . 5 ⊢ (suc 𝐴 ∈ ω → suc 𝐴 ≈ suc 𝐴) | |
4 | 2, 3 | syl 17 | . . . 4 ⊢ (𝐴 ∈ ω → suc 𝐴 ≈ suc 𝐴) |
5 | 4 | adantr 481 | . . 3 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ suc 𝐴) → suc 𝐴 ≈ suc 𝐴) |
6 | simpr 485 | . . 3 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ suc 𝐴) → 𝐵 ∈ suc 𝐴) | |
7 | dif1en 8934 | . . 3 ⊢ ((𝐴 ∈ ω ∧ suc 𝐴 ≈ suc 𝐴 ∧ 𝐵 ∈ suc 𝐴) → (suc 𝐴 ∖ {𝐵}) ≈ 𝐴) | |
8 | 1, 5, 6, 7 | syl3anc 1370 | . 2 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ suc 𝐴) → (suc 𝐴 ∖ {𝐵}) ≈ 𝐴) |
9 | nnfi 8939 | . . 3 ⊢ (𝐴 ∈ ω → 𝐴 ∈ Fin) | |
10 | ensymfib 8959 | . . 3 ⊢ (𝐴 ∈ Fin → (𝐴 ≈ (suc 𝐴 ∖ {𝐵}) ↔ (suc 𝐴 ∖ {𝐵}) ≈ 𝐴)) | |
11 | 1, 9, 10 | 3syl 18 | . 2 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ suc 𝐴) → (𝐴 ≈ (suc 𝐴 ∖ {𝐵}) ↔ (suc 𝐴 ∖ {𝐵}) ≈ 𝐴)) |
12 | 8, 11 | mpbird 256 | 1 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ suc 𝐴) → 𝐴 ≈ (suc 𝐴 ∖ {𝐵})) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 205 ∧ wa 396 ∈ wcel 2106 ∖ cdif 3885 {csn 4563 class class class wbr 5075 suc csuc 6263 ωcom 7704 ≈ cen 8719 Fincfn 8722 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1798 ax-4 1812 ax-5 1913 ax-6 1971 ax-7 2011 ax-8 2108 ax-9 2116 ax-10 2137 ax-11 2154 ax-12 2171 ax-ext 2709 ax-sep 5223 ax-nul 5230 ax-pr 5352 ax-un 7580 |
This theorem depends on definitions: df-bi 206 df-an 397 df-or 845 df-3or 1087 df-3an 1088 df-tru 1542 df-fal 1552 df-ex 1783 df-nf 1787 df-sb 2068 df-mo 2540 df-eu 2569 df-clab 2716 df-cleq 2730 df-clel 2816 df-nfc 2889 df-ne 2944 df-ral 3069 df-rex 3070 df-reu 3072 df-rab 3073 df-v 3433 df-sbc 3718 df-csb 3834 df-dif 3891 df-un 3893 df-in 3895 df-ss 3905 df-pss 3907 df-nul 4259 df-if 4462 df-pw 4537 df-sn 4564 df-pr 4566 df-op 4570 df-uni 4842 df-br 5076 df-opab 5138 df-mpt 5159 df-tr 5193 df-id 5486 df-eprel 5492 df-po 5500 df-so 5501 df-fr 5541 df-we 5543 df-xp 5592 df-rel 5593 df-cnv 5594 df-co 5595 df-dm 5596 df-rn 5597 df-res 5598 df-ima 5599 df-ord 6264 df-on 6265 df-lim 6266 df-suc 6267 df-iota 6386 df-fun 6430 df-fn 6431 df-f 6432 df-f1 6433 df-fo 6434 df-f1o 6435 df-fv 6436 df-om 7705 df-1o 8286 df-en 8723 df-fin 8726 |
This theorem is referenced by: phplem2 8980 php 8982 |
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