Theorem frind 30552

Description: The principle of founded induction. Theorem 4.4 of Don Monk's notes (see frmin 30551). This principle states that if B is a subclass of a founded class A with the property that every element of B whose initial segment is included in A is itself equal to A. Compare wfi 5420 and tfi 6699, which are special cases of this theorem that do not require the axiom of infinity to prove. (Contributed by Scott Fenton, 6-Feb-2011.) (Revised by Mario Carneiro, 26-Jun-2015.)

Assertion

Ref	Expression
frind	|- ( ( ( R Fr A /\ R Se A ) /\ ( B C_ A /\ A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) ) -> A = B )

Distinct variable groups:   y, A   y, B   y, R

Proof of Theorem frind

Step	Hyp	Ref	Expression
1		ssdif0 3741	. . . . . . 7 |- ( A C_ B <-> ( A \ B ) = (/) )
2	1	necon3bbii 2690	. . . . . 6 |- ( -. A C_ B <-> ( A \ B ) =/= (/) )
3		difss 3549	. . . . . . 7 |- ( A \ B ) C_ A
4		frmin 30551	. . . . . . . . 9 |- ( ( ( R Fr A /\ R Se A ) /\ ( ( A \ B ) C_ A /\ ( A \ B ) =/= (/) ) ) -> E. y e. ( A \ B ) Pred ( R , ( A \ B ) , y ) = (/) )
5		eldif 3400	. . . . . . . . . . . . 13 |- ( y e. ( A \ B ) <-> ( y e. A /\ -. y e. B ) )
6	5	anbi1i 709	. . . . . . . . . . . 12 |- ( ( y e. ( A \ B ) /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( ( y e. A /\ -. y e. B ) /\ Pred ( R , ( A \ B ) , y ) = (/) ) )
7		anass 661	. . . . . . . . . . . 12 |- ( ( ( y e. A /\ -. y e. B ) /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( y e. A /\ ( -. y e. B /\ Pred ( R , ( A \ B ) , y ) = (/) ) ) )
8		ancom 457	. . . . . . . . . . . . . 14 |- ( ( -. y e. B /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( Pred ( R , ( A \ B ) , y ) = (/) /\ -. y e. B ) )
9		indif2 3677	. . . . . . . . . . . . . . . . . 18 |- ( ( `' R " { y } ) i^i ( A \ B ) ) = ( ( ( `' R " { y } ) i^i A ) \ B )
10		df-pred 5387	. . . . . . . . . . . . . . . . . . 19 |- Pred ( R , ( A \ B ) , y ) = ( ( A \ B ) i^i ( `' R " { y } ) )
11		incom 3616	. . . . . . . . . . . . . . . . . . 19 |- ( ( A \ B ) i^i ( `' R " { y } ) ) = ( ( `' R " { y } ) i^i ( A \ B ) )
12	10, 11	eqtri 2493	. . . . . . . . . . . . . . . . . 18 |- Pred ( R , ( A \ B ) , y ) = ( ( `' R " { y } ) i^i ( A \ B ) )
13		df-pred 5387	. . . . . . . . . . . . . . . . . . . 20 |- Pred ( R , A , y ) = ( A i^i ( `' R " { y } ) )
14		incom 3616	. . . . . . . . . . . . . . . . . . . 20 |- ( A i^i ( `' R " { y } ) ) = ( ( `' R " { y } ) i^i A )
15	13, 14	eqtri 2493	. . . . . . . . . . . . . . . . . . 19 |- Pred ( R , A , y ) = ( ( `' R " { y } ) i^i A )
16	15	difeq1i 3536	. . . . . . . . . . . . . . . . . 18 |- ( Pred ( R , A , y ) \ B ) = ( ( ( `' R " { y } ) i^i A ) \ B )
17	9, 12, 16	3eqtr4i 2503	. . . . . . . . . . . . . . . . 17 |- Pred ( R , ( A \ B ) , y ) = ( Pred ( R , A , y ) \ B )
18	17	eqeq1i 2476	. . . . . . . . . . . . . . . 16 |- ( Pred ( R , ( A \ B ) , y ) = (/) <-> ( Pred ( R , A , y ) \ B ) = (/) )
19		ssdif0 3741	. . . . . . . . . . . . . . . 16 |- ( Pred ( R , A , y ) C_ B <-> ( Pred ( R , A , y ) \ B ) = (/) )
20	18, 19	bitr4i 260	. . . . . . . . . . . . . . 15 |- ( Pred ( R , ( A \ B ) , y ) = (/) <-> Pred ( R , A , y ) C_ B )
21	20	anbi1i 709	. . . . . . . . . . . . . 14 |- ( ( Pred ( R , ( A \ B ) , y ) = (/) /\ -. y e. B ) <-> ( Pred ( R , A , y ) C_ B /\ -. y e. B ) )
22	8, 21	bitri 257	. . . . . . . . . . . . 13 |- ( ( -. y e. B /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( Pred ( R , A , y ) C_ B /\ -. y e. B ) )
23	22	anbi2i 708	. . . . . . . . . . . 12 |- ( ( y e. A /\ ( -. y e. B /\ Pred ( R , ( A \ B ) , y ) = (/) ) ) <-> ( y e. A /\ ( Pred ( R , A , y ) C_ B /\ -. y e. B ) ) )
24	6, 7, 23	3bitri 279	. . . . . . . . . . 11 |- ( ( y e. ( A \ B ) /\ Pred ( R , ( A \ B ) , y ) = (/) ) <-> ( y e. A /\ ( Pred ( R , A , y ) C_ B /\ -. y e. B ) ) )
25	24	rexbii2 2879	. . . . . . . . . 10 |- ( E. y e. ( A \ B ) Pred ( R , ( A \ B ) , y ) = (/) <-> E. y e. A ( Pred ( R , A , y ) C_ B /\ -. y e. B ) )
26		rexanali 2839	. . . . . . . . . 10 |- ( E. y e. A ( Pred ( R , A , y ) C_ B /\ -. y e. B ) <-> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) )
27	25, 26	bitri 257	. . . . . . . . 9 |- ( E. y e. ( A \ B ) Pred ( R , ( A \ B ) , y ) = (/) <-> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) )
28	4, 27	sylib 201	. . . . . . . 8 |- ( ( ( R Fr A /\ R Se A ) /\ ( ( A \ B ) C_ A /\ ( A \ B ) =/= (/) ) ) -> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) )
29	28	ex 441	. . . . . . 7 |- ( ( R Fr A /\ R Se A ) -> ( ( ( A \ B ) C_ A /\ ( A \ B ) =/= (/) ) -> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) )
30	3, 29	mpani 690	. . . . . 6 |- ( ( R Fr A /\ R Se A ) -> ( ( A \ B ) =/= (/) -> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) )
31	2, 30	syl5bi 225	. . . . 5 |- ( ( R Fr A /\ R Se A ) -> ( -. A C_ B -> -. A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) )
32	31	con4d 108	. . . 4 |- ( ( R Fr A /\ R Se A ) -> ( A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) -> A C_ B ) )
33	32	imp 436	. . 3 |- ( ( ( R Fr A /\ R Se A ) /\ A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) -> A C_ B )
34	33	adantrl 730	. 2 |- ( ( ( R Fr A /\ R Se A ) /\ ( B C_ A /\ A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) ) -> A C_ B )
35		simprl 772	. 2 |- ( ( ( R Fr A /\ R Se A ) /\ ( B C_ A /\ A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) ) -> B C_ A )
36	34, 35	eqssd 3435	1 |- ( ( ( R Fr A /\ R Se A ) /\ ( B C_ A /\ A. y e. A ( Pred ( R , A , y ) C_ B -> y e. B ) ) ) -> A = B )

Syntax hints:   -. wn 3   -> wi 4   /\ wa 376   = wceq 1452   e. wcel 1904   =/= wne 2641   A.wral 2756   E.wrex 2757   \ cdif 3387   i^i cin 3389   C_ wss 3390   (/)c0 3722   {csn 3959   Fr wfr 4795   Se wse 4796   `'ccnv 4838   "cima 4842   Predcpred 5386

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1677  ax-4 1690  ax-5 1766  ax-6 1813  ax-7 1859  ax-8 1906  ax-9 1913  ax-10 1932  ax-11 1937  ax-12 1950  ax-13 2104  ax-ext 2451  ax-rep 4508  ax-sep 4518  ax-nul 4527  ax-pow 4579  ax-pr 4639  ax-un 6602  ax-inf2 8164

This theorem depends on definitions:  df-bi 190  df-or 377  df-an 378  df-3or 1008  df-3an 1009  df-tru 1455  df-ex 1672  df-nf 1676  df-sb 1806  df-eu 2323  df-mo 2324  df-clab 2458  df-cleq 2464  df-clel 2467  df-nfc 2601  df-ne 2643  df-ral 2761  df-rex 2762  df-reu 2763  df-rab 2765  df-v 3033  df-sbc 3256  df-csb 3350  df-dif 3393  df-un 3395  df-in 3397  df-ss 3404  df-pss 3406  df-nul 3723  df-if 3873  df-pw 3944  df-sn 3960  df-pr 3962  df-tp 3964  df-op 3966  df-uni 4191  df-iun 4271  df-br 4396  df-opab 4455  df-mpt 4456  df-tr 4491  df-eprel 4750  df-id 4754  df-po 4760  df-so 4761  df-fr 4798  df-se 4799  df-we 4800  df-xp 4845  df-rel 4846  df-cnv 4847  df-co 4848  df-dm 4849  df-rn 4850  df-res 4851  df-ima 4852  df-pred 5387  df-ord 5433  df-on 5434  df-lim 5435  df-suc 5436  df-iota 5553  df-fun 5591  df-fn 5592  df-f 5593  df-f1 5594  df-fo 5595  df-f1o 5596  df-fv 5597  df-om 6712  df-wrecs 7046  df-recs 7108  df-rdg 7146  df-trpred 30530

This theorem is referenced by:  frindi  30553  frinsg  30554