Theorem bnj69 31078

Description: Existence of a minimal element in certain classes: if R is well-founded and set-like on A, then every nonempty subclass of A has a minimal element. The proof has been taken from Chapter 4 of Don Monk's notes on Set Theory. See http://euclid.colorado.edu/~monkd/setth.pdf. (Contributed by Jonathan Ben-Naim, 3-Jun-2011.) (New usage is discouraged.)

Assertion

Ref	Expression
bnj69	|- ( ( R FrSe A /\ B C_ A /\ B =/= (/) ) -> E. x e. B A. y e. B -. y R x )

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

Proof of Theorem bnj69

Step	Hyp	Ref	Expression
1		biid 251	. 2 |- ( ( R FrSe A /\ B C_ A /\ B =/= (/) ) <-> ( R FrSe A /\ B C_ A /\ B =/= (/) ) )
2		biid 251	. 2 |- ( ( x e. B /\ y e. B /\ y R x ) <-> ( x e. B /\ y e. B /\ y R x ) )
3		biid 251	. 2 |- ( A. y e. B -. y R x <-> A. y e. B -. y R x )
4	1, 2, 3	bnj1189 31077	1 |- ( ( R FrSe A /\ B C_ A /\ B =/= (/) ) -> E. x e. B A. y e. B -. y R x )

Syntax hints:   -. wn 3   -> wi 4   /\ w3a 1037   e. wcel 1990   =/= wne 2794   A.wral 2912   E.wrex 2913   C_ wss 3574   (/)c0 3915   class class class wbr 4653   FrSe w-bnj15 30758

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-8 1992  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602  ax-rep 4771  ax-sep 4781  ax-nul 4789  ax-pow 4843  ax-pr 4906  ax-un 6949  ax-reg 8497  ax-inf2 8538

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-3or 1038  df-3an 1039  df-tru 1486  df-fal 1489  df-ex 1705  df-nf 1710  df-sb 1881  df-eu 2474  df-mo 2475  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-ne 2795  df-ral 2917  df-rex 2918  df-reu 2919  df-rab 2921  df-v 3202  df-sbc 3436  df-csb 3534  df-dif 3577  df-un 3579  df-in 3581  df-ss 3588  df-pss 3590  df-nul 3916  df-if 4087  df-pw 4160  df-sn 4178  df-pr 4180  df-tp 4182  df-op 4184  df-uni 4437  df-iun 4522  df-br 4654  df-opab 4713  df-mpt 4730  df-tr 4753  df-id 5024  df-eprel 5029  df-po 5035  df-so 5036  df-fr 5073  df-we 5075  df-xp 5120  df-rel 5121  df-cnv 5122  df-co 5123  df-dm 5124  df-rn 5125  df-res 5126  df-ima 5127  df-ord 5726  df-on 5727  df-lim 5728  df-suc 5729  df-iota 5851  df-fun 5890  df-fn 5891  df-f 5892  df-f1 5893  df-fo 5894  df-f1o 5895  df-fv 5896  df-om 7066  df-1o 7560  df-bnj17 30753  df-bnj14 30755  df-bnj13 30757  df-bnj15 30759  df-bnj18 30761  df-bnj19 30763

This theorem is referenced by:  bnj1228  31079  bnj1523  31139