Theorem phpm 6926

Description: Pigeonhole Principle. A natural number is not equinumerous to a proper subset of itself. By "proper subset" here we mean that there is an element which is in the natural number and not in the subset, or in symbols E. x x e. ( A \ B ) (which is stronger than not being equal in the absence of excluded middle). 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 6913 through phplem4 6916, nneneq 6918, and this final piece of the proof. (Contributed by NM, 29-May-1998.)

Assertion

Ref	Expression
phpm	|- ( ( A e. om /\ B C_ A /\ E. x x e. ( A \ B ) ) -> -. A ~~ B )

Distinct variable groups:   x, A   x, B

Proof of Theorem phpm

Dummy variable y is distinct from all other variables.

Step	Hyp	Ref	Expression
1		simpr 110	. . . . . 6 |- ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ A = (/) ) -> A = (/) )
2		eldifi 3285	. . . . . . . . 9 |- ( x e. ( A \ B ) -> x e. A )
3		ne0i 3457	. . . . . . . . 9 |- ( x e. A -> A =/= (/) )
4	2, 3	syl 14	. . . . . . . 8 |- ( x e. ( A \ B ) -> A =/= (/) )
5	4	neneqd 2388	. . . . . . 7 |- ( x e. ( A \ B ) -> -. A = (/) )
6	5	ad2antlr 489	. . . . . 6 |- ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ A = (/) ) -> -. A = (/) )
7	1, 6	pm2.21dd 621	. . . . 5 |- ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ A = (/) ) -> -. A ~~ B )
8		php5dom 6924	. . . . . . . . . 10 |- ( y e. om -> -. suc y ~<_ y )
9	8	ad2antlr 489	. . . . . . . . 9 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> -. suc y ~<_ y )
10		simplr 528	. . . . . . . . . 10 |- ( ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) /\ A ~~ B ) -> A = suc y )
11		simpr 110	. . . . . . . . . . 11 |- ( ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) /\ A ~~ B ) -> A ~~ B )
12		vex 2766	. . . . . . . . . . . . . . . 16 |- y e. _V
13	12	sucex 4535	. . . . . . . . . . . . . . 15 |- suc y e. _V
14		difss 3289	. . . . . . . . . . . . . . 15 |- ( suc y \ { x } ) C_ suc y
15	13, 14	ssexi 4171	. . . . . . . . . . . . . 14 |- ( suc y \ { x } ) e. _V
16		eldifn 3286	. . . . . . . . . . . . . . . 16 |- ( x e. ( A \ B ) -> -. x e. B )
17	16	ad3antlr 493	. . . . . . . . . . . . . . 15 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> -. x e. B )
18		simpllr 534	. . . . . . . . . . . . . . . . 17 |- ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) -> B C_ A )
19	18	adantr 276	. . . . . . . . . . . . . . . 16 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> B C_ A )
20		simpr 110	. . . . . . . . . . . . . . . 16 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> A = suc y )
21	19, 20	sseqtrd 3221	. . . . . . . . . . . . . . 15 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> B C_ suc y )
22		ssdif 3298	. . . . . . . . . . . . . . . 16 |- ( B C_ suc y -> ( B \ { x } ) C_ ( suc y \ { x } ) )
23		disjsn 3684	. . . . . . . . . . . . . . . . . 18 |- ( ( B i^i { x } ) = (/) <-> -. x e. B )
24		disj3 3503	. . . . . . . . . . . . . . . . . 18 |- ( ( B i^i { x } ) = (/) <-> B = ( B \ { x } ) )
25	23, 24	bitr3i 186	. . . . . . . . . . . . . . . . 17 |- ( -. x e. B <-> B = ( B \ { x } ) )
26		sseq1 3206	. . . . . . . . . . . . . . . . 17 |- ( B = ( B \ { x } ) -> ( B C_ ( suc y \ { x } ) <-> ( B \ { x } ) C_ ( suc y \ { x } ) ) )
27	25, 26	sylbi 121	. . . . . . . . . . . . . . . 16 |- ( -. x e. B -> ( B C_ ( suc y \ { x } ) <-> ( B \ { x } ) C_ ( suc y \ { x } ) ) )
28	22, 27	imbitrrid 156	. . . . . . . . . . . . . . 15 |- ( -. x e. B -> ( B C_ suc y -> B C_ ( suc y \ { x } ) ) )
29	17, 21, 28	sylc 62	. . . . . . . . . . . . . 14 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> B C_ ( suc y \ { x } ) )
30		ssdomg 6837	. . . . . . . . . . . . . 14 |- ( ( suc y \ { x } ) e. _V -> ( B C_ ( suc y \ { x } ) -> B ~<_ ( suc y \ { x } ) ) )
31	15, 29, 30	mpsyl 65	. . . . . . . . . . . . 13 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> B ~<_ ( suc y \ { x } ) )
32		simplr 528	. . . . . . . . . . . . . 14 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> y e. om )
33	2	ad3antlr 493	. . . . . . . . . . . . . . 15 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> x e. A )
34	33, 20	eleqtrd 2275	. . . . . . . . . . . . . 14 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> x e. suc y )
35		phplem3g 6917	. . . . . . . . . . . . . . 15 |- ( ( y e. om /\ x e. suc y ) -> y ~~ ( suc y \ { x } ) )
36	35	ensymd 6842	. . . . . . . . . . . . . 14 |- ( ( y e. om /\ x e. suc y ) -> ( suc y \ { x } ) ~~ y )
37	32, 34, 36	syl2anc 411	. . . . . . . . . . . . 13 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> ( suc y \ { x } ) ~~ y )
38		domentr 6850	. . . . . . . . . . . . 13 |- ( ( B ~<_ ( suc y \ { x } ) /\ ( suc y \ { x } ) ~~ y ) -> B ~<_ y )
39	31, 37, 38	syl2anc 411	. . . . . . . . . . . 12 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> B ~<_ y )
40	39	adantr 276	. . . . . . . . . . 11 |- ( ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) /\ A ~~ B ) -> B ~<_ y )
41		endomtr 6849	. . . . . . . . . . 11 |- ( ( A ~~ B /\ B ~<_ y ) -> A ~<_ y )
42	11, 40, 41	syl2anc 411	. . . . . . . . . 10 |- ( ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) /\ A ~~ B ) -> A ~<_ y )
43	10, 42	eqbrtrrd 4057	. . . . . . . . 9 |- ( ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) /\ A ~~ B ) -> suc y ~<_ y )
44	9, 43	mtand 666	. . . . . . . 8 |- ( ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) /\ A = suc y ) -> -. A ~~ B )
45	44	ex 115	. . . . . . 7 |- ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ y e. om ) -> ( A = suc y -> -. A ~~ B ) )
46	45	rexlimdva 2614	. . . . . 6 |- ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) -> ( E. y e. om A = suc y -> -. A ~~ B ) )
47	46	imp 124	. . . . 5 |- ( ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) /\ E. y e. om A = suc y ) -> -. A ~~ B )
48		nn0suc 4640	. . . . . 6 |- ( A e. om -> ( A = (/) \/ E. y e. om A = suc y ) )
49	48	ad2antrr 488	. . . . 5 |- ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) -> ( A = (/) \/ E. y e. om A = suc y ) )
50	7, 47, 49	mpjaodan 799	. . . 4 |- ( ( ( A e. om /\ B C_ A ) /\ x e. ( A \ B ) ) -> -. A ~~ B )
51	50	ex 115	. . 3 |- ( ( A e. om /\ B C_ A ) -> ( x e. ( A \ B ) -> -. A ~~ B ) )
52	51	exlimdv 1833	. 2 |- ( ( A e. om /\ B C_ A ) -> ( E. x x e. ( A \ B ) -> -. A ~~ B ) )
53	52	3impia 1202	1 |- ( ( A e. om /\ B C_ A /\ E. x x e. ( A \ B ) ) -> -. A ~~ B )

Syntax hints:   -. wn 3   -> wi 4   /\ wa 104   <-> wb 105   \/ wo 709   /\ w3a 980   = wceq 1364   E.wex 1506   e. wcel 2167   =/= wne 2367   E.wrex 2476   _Vcvv 2763   \ cdif 3154   i^i cin 3156   C_ wss 3157   (/)c0 3450   {csn 3622   class class class wbr 4033   suc csuc 4400   omcom 4626   ~~ cen 6797   ~<_ cdom 6798

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 615  ax-in2 616  ax-io 710  ax-5 1461  ax-7 1462  ax-gen 1463  ax-ie1 1507  ax-ie2 1508  ax-8 1518  ax-10 1519  ax-11 1520  ax-i12 1521  ax-bndl 1523  ax-4 1524  ax-17 1540  ax-i9 1544  ax-ial 1548  ax-i5r 1549  ax-13 2169  ax-14 2170  ax-ext 2178  ax-sep 4151  ax-nul 4159  ax-pow 4207  ax-pr 4242  ax-un 4468  ax-setind 4573  ax-iinf 4624

This theorem depends on definitions:  df-bi 117  df-dc 836  df-3or 981  df-3an 982  df-tru 1367  df-fal 1370  df-nf 1475  df-sb 1777  df-eu 2048  df-mo 2049  df-clab 2183  df-cleq 2189  df-clel 2192  df-nfc 2328  df-ne 2368  df-ral 2480  df-rex 2481  df-rab 2484  df-v 2765  df-sbc 2990  df-dif 3159  df-un 3161  df-in 3163  df-ss 3170  df-nul 3451  df-pw 3607  df-sn 3628  df-pr 3629  df-op 3631  df-uni 3840  df-int 3875  df-br 4034  df-opab 4095  df-tr 4132  df-id 4328  df-iord 4401  df-on 4403  df-suc 4406  df-iom 4627  df-xp 4669  df-rel 4670  df-cnv 4671  df-co 4672  df-dm 4673  df-rn 4674  df-res 4675  df-ima 4676  df-iota 5219  df-fun 5260  df-fn 5261  df-f 5262  df-f1 5263  df-fo 5264  df-f1o 5265  df-fv 5266  df-er 6592  df-en 6800  df-dom 6801

This theorem is referenced by:  phpelm  6927