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Mirrors > Home > MPE Home > Th. List > phplem1 | Structured version Visualization version GIF version |
Description: Lemma for Pigeonhole Principle. If we join a natural number to itself minus an element, we end up with its successor minus the same element. (Contributed by NM, 25-May-1998.) |
Ref | Expression |
---|---|
phplem1 | ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ 𝐴) → ({𝐴} ∪ (𝐴 ∖ {𝐵})) = (suc 𝐴 ∖ {𝐵})) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nnord 7582 | . . 3 ⊢ (𝐴 ∈ ω → Ord 𝐴) | |
2 | nordeq 6205 | . . . 4 ⊢ ((Ord 𝐴 ∧ 𝐵 ∈ 𝐴) → 𝐴 ≠ 𝐵) | |
3 | disjsn2 4642 | . . . 4 ⊢ (𝐴 ≠ 𝐵 → ({𝐴} ∩ {𝐵}) = ∅) | |
4 | 2, 3 | syl 17 | . . 3 ⊢ ((Ord 𝐴 ∧ 𝐵 ∈ 𝐴) → ({𝐴} ∩ {𝐵}) = ∅) |
5 | 1, 4 | sylan 582 | . 2 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ 𝐴) → ({𝐴} ∩ {𝐵}) = ∅) |
6 | undif4 4416 | . . 3 ⊢ (({𝐴} ∩ {𝐵}) = ∅ → ({𝐴} ∪ (𝐴 ∖ {𝐵})) = (({𝐴} ∪ 𝐴) ∖ {𝐵})) | |
7 | df-suc 6192 | . . . . 5 ⊢ suc 𝐴 = (𝐴 ∪ {𝐴}) | |
8 | 7 | equncomi 4131 | . . . 4 ⊢ suc 𝐴 = ({𝐴} ∪ 𝐴) |
9 | 8 | difeq1i 4095 | . . 3 ⊢ (suc 𝐴 ∖ {𝐵}) = (({𝐴} ∪ 𝐴) ∖ {𝐵}) |
10 | 6, 9 | syl6eqr 2874 | . 2 ⊢ (({𝐴} ∩ {𝐵}) = ∅ → ({𝐴} ∪ (𝐴 ∖ {𝐵})) = (suc 𝐴 ∖ {𝐵})) |
11 | 5, 10 | syl 17 | 1 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ 𝐴) → ({𝐴} ∪ (𝐴 ∖ {𝐵})) = (suc 𝐴 ∖ {𝐵})) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∧ wa 398 = wceq 1533 ∈ wcel 2110 ≠ wne 3016 ∖ cdif 3933 ∪ cun 3934 ∩ cin 3935 ∅c0 4291 {csn 4561 Ord word 6185 suc csuc 6188 ωcom 7574 |
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 1907 ax-6 1966 ax-7 2011 ax-8 2112 ax-9 2120 ax-10 2141 ax-11 2156 ax-12 2172 ax-ext 2793 ax-sep 5196 ax-nul 5203 ax-pr 5322 ax-un 7455 |
This theorem depends on definitions: df-bi 209 df-an 399 df-or 844 df-3or 1084 df-3an 1085 df-tru 1536 df-ex 1777 df-nf 1781 df-sb 2066 df-mo 2618 df-eu 2650 df-clab 2800 df-cleq 2814 df-clel 2893 df-nfc 2963 df-ne 3017 df-ral 3143 df-rex 3144 df-rab 3147 df-v 3497 df-sbc 3773 df-dif 3939 df-un 3941 df-in 3943 df-ss 3952 df-pss 3954 df-nul 4292 df-if 4468 df-sn 4562 df-pr 4564 df-tp 4566 df-op 4568 df-uni 4833 df-br 5060 df-opab 5122 df-tr 5166 df-eprel 5460 df-po 5469 df-so 5470 df-fr 5509 df-we 5511 df-ord 6189 df-on 6190 df-lim 6191 df-suc 6192 df-om 7575 |
This theorem is referenced by: phplem2 8691 |
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