Theorem php 8685

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 8680 through phplem4 8683, nneneq 8684, 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 4304	. . . . . . . 8 ⊢ ∅ ⊆ 𝐵
2		sspsstr 4033	. . . . . . . 8 ⊢ ((∅ ⊆ 𝐵 ∧ 𝐵 ⊊ 𝐴) → ∅ ⊊ 𝐴)
3	1, 2	mpan 689	. . . . . . 7 ⊢ (𝐵 ⊊ 𝐴 → ∅ ⊊ 𝐴)
4		0pss 4352	. . . . . . . 8 ⊢ (∅ ⊊ 𝐴 ↔ 𝐴 ≠ ∅)
5		df-ne 2988	. . . . . . . 8 ⊢ (𝐴 ≠ ∅ ↔ ¬ 𝐴 = ∅)
6	4, 5	bitri 278	. . . . . . 7 ⊢ (∅ ⊊ 𝐴 ↔ ¬ 𝐴 = ∅)
7	3, 6	sylib 221	. . . . . 6 ⊢ (𝐵 ⊊ 𝐴 → ¬ 𝐴 = ∅)
8		nn0suc 7586	. . . . . . 7 ⊢ (𝐴 ∈ ω → (𝐴 = ∅ ∨ ∃𝑥 ∈ ω 𝐴 = suc 𝑥))
9	8	orcanai 1000	. . . . . 6 ⊢ ((𝐴 ∈ ω ∧ ¬ 𝐴 = ∅) → ∃𝑥 ∈ ω 𝐴 = suc 𝑥)
10	7, 9	sylan2 595	. . . . 5 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊊ 𝐴) → ∃𝑥 ∈ ω 𝐴 = suc 𝑥)
11		pssnel 4378	. . . . . . . . . 10 ⊢ (𝐵 ⊊ suc 𝑥 → ∃𝑦(𝑦 ∈ suc 𝑥 ∧ ¬ 𝑦 ∈ 𝐵))
12		pssss 4023	. . . . . . . . . . . . . . . . 17 ⊢ (𝐵 ⊊ suc 𝑥 → 𝐵 ⊆ suc 𝑥)
13		ssdif 4067	. . . . . . . . . . . . . . . . . 18 ⊢ (𝐵 ⊆ suc 𝑥 → (𝐵 ∖ {𝑦}) ⊆ (suc 𝑥 ∖ {𝑦}))
14		disjsn 4607	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((𝐵 ∩ {𝑦}) = ∅ ↔ ¬ 𝑦 ∈ 𝐵)
15		disj3 4361	. . . . . . . . . . . . . . . . . . . 20 ⊢ ((𝐵 ∩ {𝑦}) = ∅ ↔ 𝐵 = (𝐵 ∖ {𝑦}))
16	14, 15	bitr3i 280	. . . . . . . . . . . . . . . . . . 19 ⊢ (¬ 𝑦 ∈ 𝐵 ↔ 𝐵 = (𝐵 ∖ {𝑦}))
17		sseq1 3940	. . . . . . . . . . . . . . . . . . 19 ⊢ (𝐵 = (𝐵 ∖ {𝑦}) → (𝐵 ⊆ (suc 𝑥 ∖ {𝑦}) ↔ (𝐵 ∖ {𝑦}) ⊆ (suc 𝑥 ∖ {𝑦})))
18	16, 17	sylbi 220	. . . . . . . . . . . . . . . . . 18 ⊢ (¬ 𝑦 ∈ 𝐵 → (𝐵 ⊆ (suc 𝑥 ∖ {𝑦}) ↔ (𝐵 ∖ {𝑦}) ⊆ (suc 𝑥 ∖ {𝑦})))
19	13, 18	syl5ibr 249	. . . . . . . . . . . . . . . . 17 ⊢ (¬ 𝑦 ∈ 𝐵 → (𝐵 ⊆ suc 𝑥 → 𝐵 ⊆ (suc 𝑥 ∖ {𝑦})))
20		vex 3444	. . . . . . . . . . . . . . . . . . . 20 ⊢ 𝑥 ∈ V
21	20	sucex 7506	. . . . . . . . . . . . . . . . . . 19 ⊢ suc 𝑥 ∈ V
22	21	difexi 5196	. . . . . . . . . . . . . . . . . 18 ⊢ (suc 𝑥 ∖ {𝑦}) ∈ V
23		ssdomg 8538	. . . . . . . . . . . . . . . . . 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 410	. . . . . . . . . . . . . . 15 ⊢ ((¬ 𝑦 ∈ 𝐵 ∧ 𝐵 ⊊ suc 𝑥) → 𝐵 ≼ (suc 𝑥 ∖ {𝑦}))
27		vex 3444	. . . . . . . . . . . . . . . . 17 ⊢ 𝑦 ∈ V
28	20, 27	phplem3 8682	. . . . . . . . . . . . . . . 16 ⊢ ((𝑥 ∈ ω ∧ 𝑦 ∈ suc 𝑥) → 𝑥 ≈ (suc 𝑥 ∖ {𝑦}))
29	28	ensymd 8543	. . . . . . . . . . . . . . 15 ⊢ ((𝑥 ∈ ω ∧ 𝑦 ∈ suc 𝑥) → (suc 𝑥 ∖ {𝑦}) ≈ 𝑥)
30		domentr 8551	. . . . . . . . . . . . . . 15 ⊢ ((𝐵 ≼ (suc 𝑥 ∖ {𝑦}) ∧ (suc 𝑥 ∖ {𝑦}) ≈ 𝑥) → 𝐵 ≼ 𝑥)
31	26, 29, 30	syl2an 598	. . . . . . . . . . . . . 14 ⊢ (((¬ 𝑦 ∈ 𝐵 ∧ 𝐵 ⊊ suc 𝑥) ∧ (𝑥 ∈ ω ∧ 𝑦 ∈ suc 𝑥)) → 𝐵 ≼ 𝑥)
32	31	exp43 440	. . . . . . . . . . . . 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 410	. . . . . . . . . . 11 ⊢ ((𝑦 ∈ suc 𝑥 ∧ ¬ 𝑦 ∈ 𝐵) → (𝐵 ⊊ suc 𝑥 → (𝑥 ∈ ω → 𝐵 ≼ 𝑥)))
35	34	exlimiv 1931	. . . . . . . . . 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 8550	. . . . . . . . . . . 12 ⊢ ((suc 𝑥 ≈ 𝐵 ∧ 𝐵 ≼ 𝑥) → suc 𝑥 ≼ 𝑥)
38		sssucid 6236	. . . . . . . . . . . . 13 ⊢ 𝑥 ⊆ suc 𝑥
39		ssdomg 8538	. . . . . . . . . . . . 13 ⊢ (suc 𝑥 ∈ V → (𝑥 ⊆ suc 𝑥 → 𝑥 ≼ suc 𝑥))
40	21, 38, 39	mp2 9	. . . . . . . . . . . 12 ⊢ 𝑥 ≼ suc 𝑥
41		sbth 8621	. . . . . . . . . . . 12 ⊢ ((suc 𝑥 ≼ 𝑥 ∧ 𝑥 ≼ suc 𝑥) → suc 𝑥 ≈ 𝑥)
42	37, 40, 41	sylancl 589	. . . . . . . . . . 11 ⊢ ((suc 𝑥 ≈ 𝐵 ∧ 𝐵 ≼ 𝑥) → suc 𝑥 ≈ 𝑥)
43	42	expcom 417	. . . . . . . . . 10 ⊢ (𝐵 ≼ 𝑥 → (suc 𝑥 ≈ 𝐵 → suc 𝑥 ≈ 𝑥))
44		peano2b 7576	. . . . . . . . . . . . 13 ⊢ (𝑥 ∈ ω ↔ suc 𝑥 ∈ ω)
45		nnord 7568	. . . . . . . . . . . . 13 ⊢ (suc 𝑥 ∈ ω → Ord suc 𝑥)
46	44, 45	sylbi 220	. . . . . . . . . . . 12 ⊢ (𝑥 ∈ ω → Ord suc 𝑥)
47	20	sucid 6238	. . . . . . . . . . . 12 ⊢ 𝑥 ∈ suc 𝑥
48		nordeq 6178	. . . . . . . . . . . 12 ⊢ ((Ord suc 𝑥 ∧ 𝑥 ∈ suc 𝑥) → suc 𝑥 ≠ 𝑥)
49	46, 47, 48	sylancl 589	. . . . . . . . . . 11 ⊢ (𝑥 ∈ ω → suc 𝑥 ≠ 𝑥)
50		nneneq 8684	. . . . . . . . . . . . . 14 ⊢ ((suc 𝑥 ∈ ω ∧ 𝑥 ∈ ω) → (suc 𝑥 ≈ 𝑥 ↔ suc 𝑥 = 𝑥))
51	44, 50	sylanb 584	. . . . . . . . . . . . 13 ⊢ ((𝑥 ∈ ω ∧ 𝑥 ∈ ω) → (suc 𝑥 ≈ 𝑥 ↔ suc 𝑥 = 𝑥))
52	51	anidms 570	. . . . . . . . . . . 12 ⊢ (𝑥 ∈ ω → (suc 𝑥 ≈ 𝑥 ↔ suc 𝑥 = 𝑥))
53	52	necon3bbid 3024	. . . . . . . . . . 11 ⊢ (𝑥 ∈ ω → (¬ suc 𝑥 ≈ 𝑥 ↔ suc 𝑥 ≠ 𝑥))
54	49, 53	mpbird 260	. . . . . . . . . 10 ⊢ (𝑥 ∈ ω → ¬ suc 𝑥 ≈ 𝑥)
55	43, 54	nsyli 160	. . . . . . . . 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 4016	. . . . . . . 8 ⊢ (𝐴 = suc 𝑥 → (𝐵 ⊊ 𝐴 ↔ 𝐵 ⊊ suc 𝑥))
59		breq1 5033	. . . . . . . . 9 ⊢ (𝐴 = suc 𝑥 → (𝐴 ≈ 𝐵 ↔ suc 𝑥 ≈ 𝐵))
60	59	notbid 321	. . . . . . . 8 ⊢ (𝐴 = suc 𝑥 → (¬ 𝐴 ≈ 𝐵 ↔ ¬ suc 𝑥 ≈ 𝐵))
61	58, 60	imbi12d 348	. . . . . . 7 ⊢ (𝐴 = suc 𝑥 → ((𝐵 ⊊ 𝐴 → ¬ 𝐴 ≈ 𝐵) ↔ (𝐵 ⊊ suc 𝑥 → ¬ suc 𝑥 ≈ 𝐵)))
62	57, 61	syl5ibrcom 250	. . . . . 6 ⊢ (𝑥 ∈ ω → (𝐴 = suc 𝑥 → (𝐵 ⊊ 𝐴 → ¬ 𝐴 ≈ 𝐵)))
63	62	rexlimiv 3239	. . . . 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 416	. . 3 ⊢ (𝐴 ∈ ω → (𝐵 ⊊ 𝐴 → (𝐵 ⊊ 𝐴 → ¬ 𝐴 ≈ 𝐵)))
66	65	pm2.43d 53	. 2 ⊢ (𝐴 ∈ ω → (𝐵 ⊊ 𝐴 → ¬ 𝐴 ≈ 𝐵))
67	66	imp 410	1 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ⊊ 𝐴) → ¬ 𝐴 ≈ 𝐵)

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 209   ∧ wa 399   = wceq 1538  ∃wex 1781   ∈ wcel 2111   ≠ wne 2987  ∃wrex 3107  Vcvv 3441   ∖ cdif 3878   ∩ cin 3880   ⊆ wss 3881   ⊊ wpss 3882  ∅c0 4243  {csn 4525   class class class wbr 5030  Ord word 6158  suc csuc 6161  ωcom 7560   ≈ cen 8489   ≼ cdom 8490

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1911  ax-6 1970  ax-7 2015  ax-8 2113  ax-9 2121  ax-10 2142  ax-11 2158  ax-12 2175  ax-ext 2770  ax-sep 5167  ax-nul 5174  ax-pow 5231  ax-pr 5295  ax-un 7441

This theorem depends on definitions:  df-bi 210  df-an 400  df-or 845  df-3or 1085  df-3an 1086  df-tru 1541  df-ex 1782  df-nf 1786  df-sb 2070  df-mo 2598  df-eu 2629  df-clab 2777  df-cleq 2791  df-clel 2870  df-nfc 2938  df-ne 2988  df-ral 3111  df-rex 3112  df-rab 3115  df-v 3443  df-sbc 3721  df-dif 3884  df-un 3886  df-in 3888  df-ss 3898  df-pss 3900  df-nul 4244  df-if 4426  df-pw 4499  df-sn 4526  df-pr 4528  df-tp 4530  df-op 4532  df-uni 4801  df-br 5031  df-opab 5093  df-tr 5137  df-id 5425  df-eprel 5430  df-po 5438  df-so 5439  df-fr 5478  df-we 5480  df-xp 5525  df-rel 5526  df-cnv 5527  df-co 5528  df-dm 5529  df-rn 5530  df-res 5531  df-ima 5532  df-ord 6162  df-on 6163  df-lim 6164  df-suc 6165  df-iota 6283  df-fun 6326  df-fn 6327  df-f 6328  df-f1 6329  df-fo 6330  df-f1o 6331  df-fv 6332  df-om 7561  df-er 8272  df-en 8493  df-dom 8494

This theorem is referenced by:  php2  8686  php3  8687  rr-phpd  40916