Theorem php 8434

Description: Pigeonhole Principle. A natural number is not equinumerous to a proper subset of itself. Theorem (Pigeonhole Principle) of [Enderton] p. 134. The theorem is so-called because you can't put n + 1 pigeons into n holes (if each hole holds only one pigeon). The proof consists of lemmas phplem1 8429 through phplem4 8432, nneneq 8433, and this final piece of the proof. (Contributed by NM, 29-May-1998.)

Assertion

Ref	Expression
php	⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊊ 𝐴) → ¬ 𝐴 ≈ 𝐵)

Proof of Theorem php

Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		0ss 4198	. . . . . . . 8 ⊢ ∅ ⊆ 𝐵
2		sspsstr 3934	. . . . . . . 8 ⊢ ((∅ ⊆ 𝐵 ∧ 𝐵 ⊊ 𝐴) → ∅ ⊊ 𝐴)
3	1, 2	mpan 680	. . . . . . 7 ⊢ (𝐵 ⊊ 𝐴 → ∅ ⊊ 𝐴)
4		0pss 4239	. . . . . . . 8 ⊢ (∅ ⊊ 𝐴 ↔ 𝐴 ≠ ∅)
5		df-ne 2970	. . . . . . . 8 ⊢ (𝐴 ≠ ∅ ↔ ¬ 𝐴 = ∅)
6	4, 5	bitri 267	. . . . . . 7 ⊢ (∅ ⊊ 𝐴 ↔ ¬ 𝐴 = ∅)
7	3, 6	sylib 210	. . . . . 6 ⊢ (𝐵 ⊊ 𝐴 → ¬ 𝐴 = ∅)
8		nn0suc 7370	. . . . . . 7 ⊢ (𝐴 ∈ ω → (𝐴 = ∅ ∨ ∃𝑥 ∈ ω 𝐴 = suc 𝑥))
9	8	orcanai 988	. . . . . 6 ⊢ ((𝐴 ∈ ω ∧ ¬ 𝐴 = ∅) → ∃𝑥 ∈ ω 𝐴 = suc 𝑥)
10	7, 9	sylan2 586	. . . . 5 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊊ 𝐴) → ∃𝑥 ∈ ω 𝐴 = suc 𝑥)
11		pssnel 4263	. . . . . . . . . 10 ⊢ (𝐵 ⊊ suc 𝑥 → ∃𝑦(𝑦 ∈ suc 𝑥 ∧ ¬ 𝑦 ∈ 𝐵))
12		pssss 3924	. . . . . . . . . . . . . . . . 17 ⊢ (𝐵 ⊊ suc 𝑥 → 𝐵 ⊆ suc 𝑥)
13		ssdif 3968	. . . . . . . . . . . . . . . . . 18 ⊢ (𝐵 ⊆ suc 𝑥 → (𝐵 ∖ {𝑦}) ⊆ (suc 𝑥 ∖ {𝑦}))
14		disjsn 4478	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((𝐵 ∩ {𝑦}) = ∅ ↔ ¬ 𝑦 ∈ 𝐵)
15		disj3 4246	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((𝐵 ∩ {𝑦}) = ∅ ↔ 𝐵 = (𝐵 ∖ {𝑦}))
16	14, 15	bitr3i 269	. . . . . . . . . . . . . . . . . . 19 ⊢ (¬ 𝑦 ∈ 𝐵 ↔ 𝐵 = (𝐵 ∖ {𝑦}))
17		sseq1 3845	. . . . . . . . . . . . . . . . . . 19 ⊢ (𝐵 = (𝐵 ∖ {𝑦}) → (𝐵 ⊆ (suc 𝑥 ∖ {𝑦}) ↔ (𝐵 ∖ {𝑦}) ⊆ (suc 𝑥 ∖ {𝑦})))
18	16, 17	sylbi 209	. . . . . . . . . . . . . . . . . 18 ⊢ (¬ 𝑦 ∈ 𝐵 → (𝐵 ⊆ (suc 𝑥 ∖ {𝑦}) ↔ (𝐵 ∖ {𝑦}) ⊆ (suc 𝑥 ∖ {𝑦})))
19	13, 18	syl5ibr 238	. . . . . . . . . . . . . . . . 17 ⊢ (¬ 𝑦 ∈ 𝐵 → (𝐵 ⊆ suc 𝑥 → 𝐵 ⊆ (suc 𝑥 ∖ {𝑦})))
20		vex 3401	. . . . . . . . . . . . . . . . . . . 20 ⊢ 𝑥 ∈ V
21	20	sucex 7291	. . . . . . . . . . . . . . . . . . 19 ⊢ suc 𝑥 ∈ V
22	21	difexi 5048	. . . . . . . . . . . . . . . . . 18 ⊢ (suc 𝑥 ∖ {𝑦}) ∈ V
23		ssdomg 8289	. . . . . . . . . . . . . . . . . 18 ⊢ ((suc 𝑥 ∖ {𝑦}) ∈ V → (𝐵 ⊆ (suc 𝑥 ∖ {𝑦}) → 𝐵 ≼ (suc 𝑥 ∖ {𝑦})))
24	22, 23	ax-mp 5	. . . . . . . . . . . . . . . . 17 ⊢ (𝐵 ⊆ (suc 𝑥 ∖ {𝑦}) → 𝐵 ≼ (suc 𝑥 ∖ {𝑦}))
25	12, 19, 24	syl56 36	. . . . . . . . . . . . . . . 16 ⊢ (¬ 𝑦 ∈ 𝐵 → (𝐵 ⊊ suc 𝑥 → 𝐵 ≼ (suc 𝑥 ∖ {𝑦})))
26	25	imp 397	. . . . . . . . . . . . . . 15 ⊢ ((¬ 𝑦 ∈ 𝐵 ∧ 𝐵 ⊊ suc 𝑥) → 𝐵 ≼ (suc 𝑥 ∖ {𝑦}))
27		vex 3401	. . . . . . . . . . . . . . . . 17 ⊢ 𝑦 ∈ V
28	20, 27	phplem3 8431	. . . . . . . . . . . . . . . 16 ⊢ ((𝑥 ∈ ω ∧ 𝑦 ∈ suc 𝑥) → 𝑥 ≈ (suc 𝑥 ∖ {𝑦}))
29	28	ensymd 8294	. . . . . . . . . . . . . . 15 ⊢ ((𝑥 ∈ ω ∧ 𝑦 ∈ suc 𝑥) → (suc 𝑥 ∖ {𝑦}) ≈ 𝑥)
30		domentr 8302	. . . . . . . . . . . . . . 15 ⊢ ((𝐵 ≼ (suc 𝑥 ∖ {𝑦}) ∧ (suc 𝑥 ∖ {𝑦}) ≈ 𝑥) → 𝐵 ≼ 𝑥)
31	26, 29, 30	syl2an 589	. . . . . . . . . . . . . 14 ⊢ (((¬ 𝑦 ∈ 𝐵 ∧ 𝐵 ⊊ suc 𝑥) ∧ (𝑥 ∈ ω ∧ 𝑦 ∈ suc 𝑥)) → 𝐵 ≼ 𝑥)
32	31	exp43 429	. . . . . . . . . . . . 13 ⊢ (¬ 𝑦 ∈ 𝐵 → (𝐵 ⊊ suc 𝑥 → (𝑥 ∈ ω → (𝑦 ∈ suc 𝑥 → 𝐵 ≼ 𝑥))))
33	32	com4r 94	. . . . . . . . . . . 12 ⊢ (𝑦 ∈ suc 𝑥 → (¬ 𝑦 ∈ 𝐵 → (𝐵 ⊊ suc 𝑥 → (𝑥 ∈ ω → 𝐵 ≼ 𝑥))))
34	33	imp 397	. . . . . . . . . . 11 ⊢ ((𝑦 ∈ suc 𝑥 ∧ ¬ 𝑦 ∈ 𝐵) → (𝐵 ⊊ suc 𝑥 → (𝑥 ∈ ω → 𝐵 ≼ 𝑥)))
35	34	exlimiv 1973	. . . . . . . . . 10 ⊢ (∃𝑦(𝑦 ∈ suc 𝑥 ∧ ¬ 𝑦 ∈ 𝐵) → (𝐵 ⊊ suc 𝑥 → (𝑥 ∈ ω → 𝐵 ≼ 𝑥)))
36	11, 35	mpcom 38	. . . . . . . . 9 ⊢ (𝐵 ⊊ suc 𝑥 → (𝑥 ∈ ω → 𝐵 ≼ 𝑥))
37		endomtr 8301	. . . . . . . . . . . 12 ⊢ ((suc 𝑥 ≈ 𝐵 ∧ 𝐵 ≼ 𝑥) → suc 𝑥 ≼ 𝑥)
38		sssucid 6055	. . . . . . . . . . . . 13 ⊢ 𝑥 ⊆ suc 𝑥
39		ssdomg 8289	. . . . . . . . . . . . 13 ⊢ (suc 𝑥 ∈ V → (𝑥 ⊆ suc 𝑥 → 𝑥 ≼ suc 𝑥))
40	21, 38, 39	mp2 9	. . . . . . . . . . . 12 ⊢ 𝑥 ≼ suc 𝑥
41		sbth 8370	. . . . . . . . . . . 12 ⊢ ((suc 𝑥 ≼ 𝑥 ∧ 𝑥 ≼ suc 𝑥) → suc 𝑥 ≈ 𝑥)
42	37, 40, 41	sylancl 580	. . . . . . . . . . 11 ⊢ ((suc 𝑥 ≈ 𝐵 ∧ 𝐵 ≼ 𝑥) → suc 𝑥 ≈ 𝑥)
43	42	expcom 404	. . . . . . . . . 10 ⊢ (𝐵 ≼ 𝑥 → (suc 𝑥 ≈ 𝐵 → suc 𝑥 ≈ 𝑥))
44		peano2b 7361	. . . . . . . . . . . . 13 ⊢ (𝑥 ∈ ω ↔ suc 𝑥 ∈ ω)
45		nnord 7353	. . . . . . . . . . . . 13 ⊢ (suc 𝑥 ∈ ω → Ord suc 𝑥)
46	44, 45	sylbi 209	. . . . . . . . . . . 12 ⊢ (𝑥 ∈ ω → Ord suc 𝑥)
47	20	sucid 6057	. . . . . . . . . . . 12 ⊢ 𝑥 ∈ suc 𝑥
48		nordeq 5997	. . . . . . . . . . . 12 ⊢ ((Ord suc 𝑥 ∧ 𝑥 ∈ suc 𝑥) → suc 𝑥 ≠ 𝑥)
49	46, 47, 48	sylancl 580	. . . . . . . . . . 11 ⊢ (𝑥 ∈ ω → suc 𝑥 ≠ 𝑥)
50		nneneq 8433	. . . . . . . . . . . . . 14 ⊢ ((suc 𝑥 ∈ ω ∧ 𝑥 ∈ ω) → (suc 𝑥 ≈ 𝑥 ↔ suc 𝑥 = 𝑥))
51	44, 50	sylanb 576	. . . . . . . . . . . . 13 ⊢ ((𝑥 ∈ ω ∧ 𝑥 ∈ ω) → (suc 𝑥 ≈ 𝑥 ↔ suc 𝑥 = 𝑥))
52	51	anidms 562	. . . . . . . . . . . 12 ⊢ (𝑥 ∈ ω → (suc 𝑥 ≈ 𝑥 ↔ suc 𝑥 = 𝑥))
53	52	necon3bbid 3006	. . . . . . . . . . 11 ⊢ (𝑥 ∈ ω → (¬ suc 𝑥 ≈ 𝑥 ↔ suc 𝑥 ≠ 𝑥))
54	49, 53	mpbird 249	. . . . . . . . . 10 ⊢ (𝑥 ∈ ω → ¬ suc 𝑥 ≈ 𝑥)
55	43, 54	nsyli 157	. . . . . . . . 9 ⊢ (𝐵 ≼ 𝑥 → (𝑥 ∈ ω → ¬ suc 𝑥 ≈ 𝐵))
56	36, 55	syli 39	. . . . . . . 8 ⊢ (𝐵 ⊊ suc 𝑥 → (𝑥 ∈ ω → ¬ suc 𝑥 ≈ 𝐵))
57	56	com12 32	. . . . . . 7 ⊢ (𝑥 ∈ ω → (𝐵 ⊊ suc 𝑥 → ¬ suc 𝑥 ≈ 𝐵))
58		psseq2 3917	. . . . . . . 8 ⊢ (𝐴 = suc 𝑥 → (𝐵 ⊊ 𝐴 ↔ 𝐵 ⊊ suc 𝑥))
59		breq1 4891	. . . . . . . . 9 ⊢ (𝐴 = suc 𝑥 → (𝐴 ≈ 𝐵 ↔ suc 𝑥 ≈ 𝐵))
60	59	notbid 310	. . . . . . . 8 ⊢ (𝐴 = suc 𝑥 → (¬ 𝐴 ≈ 𝐵 ↔ ¬ suc 𝑥 ≈ 𝐵))
61	58, 60	imbi12d 336	. . . . . . 7 ⊢ (𝐴 = suc 𝑥 → ((𝐵 ⊊ 𝐴 → ¬ 𝐴 ≈ 𝐵) ↔ (𝐵 ⊊ suc 𝑥 → ¬ suc 𝑥 ≈ 𝐵)))
62	57, 61	syl5ibrcom 239	. . . . . 6 ⊢ (𝑥 ∈ ω → (𝐴 = suc 𝑥 → (𝐵 ⊊ 𝐴 → ¬ 𝐴 ≈ 𝐵)))
63	62	rexlimiv 3209	. . . . 5 ⊢ (∃𝑥 ∈ ω 𝐴 = suc 𝑥 → (𝐵 ⊊ 𝐴 → ¬ 𝐴 ≈ 𝐵))
64	10, 63	syl 17	. . . 4 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊊ 𝐴) → (𝐵 ⊊ 𝐴 → ¬ 𝐴 ≈ 𝐵))
65	64	ex 403	. . 3 ⊢ (𝐴 ∈ ω → (𝐵 ⊊ 𝐴 → (𝐵 ⊊ 𝐴 → ¬ 𝐴 ≈ 𝐵)))
66	65	pm2.43d 53	. 2 ⊢ (𝐴 ∈ ω → (𝐵 ⊊ 𝐴 → ¬ 𝐴 ≈ 𝐵))
67	66	imp 397	1 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊊ 𝐴) → ¬ 𝐴 ≈ 𝐵)

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 198   ∧ wa 386   = wceq 1601  ∃wex 1823   ∈ wcel 2107   ≠ wne 2969  ∃wrex 3091  Vcvv 3398   ∖ cdif 3789   ∩ cin 3791   ⊆ wss 3792   ⊊ wpss 3793  ∅c0 4141  {csn 4398   class class class wbr 4888  Ord word 5977  suc csuc 5980  ωcom 7345   ≈ cen 8240   ≼ cdom 8241

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1839  ax-4 1853  ax-5 1953  ax-6 2021  ax-7 2055  ax-8 2109  ax-9 2116  ax-10 2135  ax-11 2150  ax-12 2163  ax-13 2334  ax-ext 2754  ax-sep 5019  ax-nul 5027  ax-pow 5079  ax-pr 5140  ax-un 7228

This theorem depends on definitions:  df-bi 199  df-an 387  df-or 837  df-3or 1072  df-3an 1073  df-tru 1605  df-ex 1824  df-nf 1828  df-sb 2012  df-mo 2551  df-eu 2587  df-clab 2764  df-cleq 2770  df-clel 2774  df-nfc 2921  df-ne 2970  df-ral 3095  df-rex 3096  df-rab 3099  df-v 3400  df-sbc 3653  df-dif 3795  df-un 3797  df-in 3799  df-ss 3806  df-pss 3808  df-nul 4142  df-if 4308  df-pw 4381  df-sn 4399  df-pr 4401  df-tp 4403  df-op 4405  df-uni 4674  df-br 4889  df-opab 4951  df-tr 4990  df-id 5263  df-eprel 5268  df-po 5276  df-so 5277  df-fr 5316  df-we 5318  df-xp 5363  df-rel 5364  df-cnv 5365  df-co 5366  df-dm 5367  df-rn 5368  df-res 5369  df-ima 5370  df-ord 5981  df-on 5982  df-lim 5983  df-suc 5984  df-iota 6101  df-fun 6139  df-fn 6140  df-f 6141  df-f1 6142  df-fo 6143  df-f1o 6144  df-fv 6145  df-om 7346  df-er 8028  df-en 8244  df-dom 8245

This theorem is referenced by:  php2  8435  php3  8436