| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							isfi | 
							 |-  ( A e. Fin <-> E. x e. _om A ~~ x )  | 
						
						
							| 2 | 
							
								
							 | 
							relen | 
							 |-  Rel ~~  | 
						
						
							| 3 | 
							
								2
							 | 
							brrelex1i | 
							 |-  ( A ~~ x -> A e. _V )  | 
						
						
							| 4 | 
							
								
							 | 
							pssss | 
							 |-  ( B C. A -> B C_ A )  | 
						
						
							| 5 | 
							
								
							 | 
							ssdomg | 
							 |-  ( A e. _V -> ( B C_ A -> B ~<_ A ) )  | 
						
						
							| 6 | 
							
								5
							 | 
							imp | 
							 |-  ( ( A e. _V /\ B C_ A ) -> B ~<_ A )  | 
						
						
							| 7 | 
							
								3 4 6
							 | 
							syl2an | 
							 |-  ( ( A ~~ x /\ B C. A ) -> B ~<_ A )  | 
						
						
							| 8 | 
							
								7
							 | 
							adantll | 
							 |-  ( ( ( x e. _om /\ A ~~ x ) /\ B C. A ) -> B ~<_ A )  | 
						
						
							| 9 | 
							
								
							 | 
							bren | 
							 |-  ( A ~~ x <-> E. f f : A -1-1-onto-> x )  | 
						
						
							| 10 | 
							
								
							 | 
							imass2 | 
							 |-  ( B C_ A -> ( f " B ) C_ ( f " A ) )  | 
						
						
							| 11 | 
							
								4 10
							 | 
							syl | 
							 |-  ( B C. A -> ( f " B ) C_ ( f " A ) )  | 
						
						
							| 12 | 
							
								11
							 | 
							adantl | 
							 |-  ( ( f : A -1-1-onto-> x /\ B C. A ) -> ( f " B ) C_ ( f " A ) )  | 
						
						
							| 13 | 
							
								
							 | 
							pssnel | 
							 |-  ( B C. A -> E. y ( y e. A /\ -. y e. B ) )  | 
						
						
							| 14 | 
							
								
							 | 
							eldif | 
							 |-  ( y e. ( A \ B ) <-> ( y e. A /\ -. y e. B ) )  | 
						
						
							| 15 | 
							
								
							 | 
							f1ofn | 
							 |-  ( f : A -1-1-onto-> x -> f Fn A )  | 
						
						
							| 16 | 
							
								
							 | 
							difss | 
							 |-  ( A \ B ) C_ A  | 
						
						
							| 17 | 
							
								
							 | 
							fnfvima | 
							 |-  ( ( f Fn A /\ ( A \ B ) C_ A /\ y e. ( A \ B ) ) -> ( f ` y ) e. ( f " ( A \ B ) ) )  | 
						
						
							| 18 | 
							
								17
							 | 
							3expia | 
							 |-  ( ( f Fn A /\ ( A \ B ) C_ A ) -> ( y e. ( A \ B ) -> ( f ` y ) e. ( f " ( A \ B ) ) ) )  | 
						
						
							| 19 | 
							
								15 16 18
							 | 
							sylancl | 
							 |-  ( f : A -1-1-onto-> x -> ( y e. ( A \ B ) -> ( f ` y ) e. ( f " ( A \ B ) ) ) )  | 
						
						
							| 20 | 
							
								
							 | 
							dff1o3 | 
							 |-  ( f : A -1-1-onto-> x <-> ( f : A -onto-> x /\ Fun `' f ) )  | 
						
						
							| 21 | 
							
								
							 | 
							imadif | 
							 |-  ( Fun `' f -> ( f " ( A \ B ) ) = ( ( f " A ) \ ( f " B ) ) )  | 
						
						
							| 22 | 
							
								20 21
							 | 
							simplbiim | 
							 |-  ( f : A -1-1-onto-> x -> ( f " ( A \ B ) ) = ( ( f " A ) \ ( f " B ) ) )  | 
						
						
							| 23 | 
							
								22
							 | 
							eleq2d | 
							 |-  ( f : A -1-1-onto-> x -> ( ( f ` y ) e. ( f " ( A \ B ) ) <-> ( f ` y ) e. ( ( f " A ) \ ( f " B ) ) ) )  | 
						
						
							| 24 | 
							
								19 23
							 | 
							sylibd | 
							 |-  ( f : A -1-1-onto-> x -> ( y e. ( A \ B ) -> ( f ` y ) e. ( ( f " A ) \ ( f " B ) ) ) )  | 
						
						
							| 25 | 
							
								
							 | 
							n0i | 
							 |-  ( ( f ` y ) e. ( ( f " A ) \ ( f " B ) ) -> -. ( ( f " A ) \ ( f " B ) ) = (/) )  | 
						
						
							| 26 | 
							
								24 25
							 | 
							syl6 | 
							 |-  ( f : A -1-1-onto-> x -> ( y e. ( A \ B ) -> -. ( ( f " A ) \ ( f " B ) ) = (/) ) )  | 
						
						
							| 27 | 
							
								14 26
							 | 
							biimtrrid | 
							 |-  ( f : A -1-1-onto-> x -> ( ( y e. A /\ -. y e. B ) -> -. ( ( f " A ) \ ( f " B ) ) = (/) ) )  | 
						
						
							| 28 | 
							
								27
							 | 
							exlimdv | 
							 |-  ( f : A -1-1-onto-> x -> ( E. y ( y e. A /\ -. y e. B ) -> -. ( ( f " A ) \ ( f " B ) ) = (/) ) )  | 
						
						
							| 29 | 
							
								28
							 | 
							imp | 
							 |-  ( ( f : A -1-1-onto-> x /\ E. y ( y e. A /\ -. y e. B ) ) -> -. ( ( f " A ) \ ( f " B ) ) = (/) )  | 
						
						
							| 30 | 
							
								13 29
							 | 
							sylan2 | 
							 |-  ( ( f : A -1-1-onto-> x /\ B C. A ) -> -. ( ( f " A ) \ ( f " B ) ) = (/) )  | 
						
						
							| 31 | 
							
								
							 | 
							ssdif0 | 
							 |-  ( ( f " A ) C_ ( f " B ) <-> ( ( f " A ) \ ( f " B ) ) = (/) )  | 
						
						
							| 32 | 
							
								30 31
							 | 
							sylnibr | 
							 |-  ( ( f : A -1-1-onto-> x /\ B C. A ) -> -. ( f " A ) C_ ( f " B ) )  | 
						
						
							| 33 | 
							
								
							 | 
							dfpss3 | 
							 |-  ( ( f " B ) C. ( f " A ) <-> ( ( f " B ) C_ ( f " A ) /\ -. ( f " A ) C_ ( f " B ) ) )  | 
						
						
							| 34 | 
							
								12 32 33
							 | 
							sylanbrc | 
							 |-  ( ( f : A -1-1-onto-> x /\ B C. A ) -> ( f " B ) C. ( f " A ) )  | 
						
						
							| 35 | 
							
								
							 | 
							imadmrn | 
							 |-  ( f " dom f ) = ran f  | 
						
						
							| 36 | 
							
								
							 | 
							f1odm | 
							 |-  ( f : A -1-1-onto-> x -> dom f = A )  | 
						
						
							| 37 | 
							
								36
							 | 
							imaeq2d | 
							 |-  ( f : A -1-1-onto-> x -> ( f " dom f ) = ( f " A ) )  | 
						
						
							| 38 | 
							
								
							 | 
							f1ofo | 
							 |-  ( f : A -1-1-onto-> x -> f : A -onto-> x )  | 
						
						
							| 39 | 
							
								
							 | 
							forn | 
							 |-  ( f : A -onto-> x -> ran f = x )  | 
						
						
							| 40 | 
							
								38 39
							 | 
							syl | 
							 |-  ( f : A -1-1-onto-> x -> ran f = x )  | 
						
						
							| 41 | 
							
								35 37 40
							 | 
							3eqtr3a | 
							 |-  ( f : A -1-1-onto-> x -> ( f " A ) = x )  | 
						
						
							| 42 | 
							
								41
							 | 
							psseq2d | 
							 |-  ( f : A -1-1-onto-> x -> ( ( f " B ) C. ( f " A ) <-> ( f " B ) C. x ) )  | 
						
						
							| 43 | 
							
								42
							 | 
							adantr | 
							 |-  ( ( f : A -1-1-onto-> x /\ B C. A ) -> ( ( f " B ) C. ( f " A ) <-> ( f " B ) C. x ) )  | 
						
						
							| 44 | 
							
								34 43
							 | 
							mpbid | 
							 |-  ( ( f : A -1-1-onto-> x /\ B C. A ) -> ( f " B ) C. x )  | 
						
						
							| 45 | 
							
								
							 | 
							php | 
							 |-  ( ( x e. _om /\ ( f " B ) C. x ) -> -. x ~~ ( f " B ) )  | 
						
						
							| 46 | 
							
								44 45
							 | 
							sylan2 | 
							 |-  ( ( x e. _om /\ ( f : A -1-1-onto-> x /\ B C. A ) ) -> -. x ~~ ( f " B ) )  | 
						
						
							| 47 | 
							
								
							 | 
							f1of1 | 
							 |-  ( f : A -1-1-onto-> x -> f : A -1-1-> x )  | 
						
						
							| 48 | 
							
								
							 | 
							f1ores | 
							 |-  ( ( f : A -1-1-> x /\ B C_ A ) -> ( f |` B ) : B -1-1-onto-> ( f " B ) )  | 
						
						
							| 49 | 
							
								47 4 48
							 | 
							syl2an | 
							 |-  ( ( f : A -1-1-onto-> x /\ B C. A ) -> ( f |` B ) : B -1-1-onto-> ( f " B ) )  | 
						
						
							| 50 | 
							
								
							 | 
							vex | 
							 |-  f e. _V  | 
						
						
							| 51 | 
							
								50
							 | 
							resex | 
							 |-  ( f |` B ) e. _V  | 
						
						
							| 52 | 
							
								
							 | 
							f1oeq1 | 
							 |-  ( y = ( f |` B ) -> ( y : B -1-1-onto-> ( f " B ) <-> ( f |` B ) : B -1-1-onto-> ( f " B ) ) )  | 
						
						
							| 53 | 
							
								51 52
							 | 
							spcev | 
							 |-  ( ( f |` B ) : B -1-1-onto-> ( f " B ) -> E. y y : B -1-1-onto-> ( f " B ) )  | 
						
						
							| 54 | 
							
								
							 | 
							bren | 
							 |-  ( B ~~ ( f " B ) <-> E. y y : B -1-1-onto-> ( f " B ) )  | 
						
						
							| 55 | 
							
								53 54
							 | 
							sylibr | 
							 |-  ( ( f |` B ) : B -1-1-onto-> ( f " B ) -> B ~~ ( f " B ) )  | 
						
						
							| 56 | 
							
								49 55
							 | 
							syl | 
							 |-  ( ( f : A -1-1-onto-> x /\ B C. A ) -> B ~~ ( f " B ) )  | 
						
						
							| 57 | 
							
								
							 | 
							entr | 
							 |-  ( ( x ~~ B /\ B ~~ ( f " B ) ) -> x ~~ ( f " B ) )  | 
						
						
							| 58 | 
							
								57
							 | 
							expcom | 
							 |-  ( B ~~ ( f " B ) -> ( x ~~ B -> x ~~ ( f " B ) ) )  | 
						
						
							| 59 | 
							
								56 58
							 | 
							syl | 
							 |-  ( ( f : A -1-1-onto-> x /\ B C. A ) -> ( x ~~ B -> x ~~ ( f " B ) ) )  | 
						
						
							| 60 | 
							
								59
							 | 
							adantl | 
							 |-  ( ( x e. _om /\ ( f : A -1-1-onto-> x /\ B C. A ) ) -> ( x ~~ B -> x ~~ ( f " B ) ) )  | 
						
						
							| 61 | 
							
								46 60
							 | 
							mtod | 
							 |-  ( ( x e. _om /\ ( f : A -1-1-onto-> x /\ B C. A ) ) -> -. x ~~ B )  | 
						
						
							| 62 | 
							
								61
							 | 
							exp32 | 
							 |-  ( x e. _om -> ( f : A -1-1-onto-> x -> ( B C. A -> -. x ~~ B ) ) )  | 
						
						
							| 63 | 
							
								62
							 | 
							exlimdv | 
							 |-  ( x e. _om -> ( E. f f : A -1-1-onto-> x -> ( B C. A -> -. x ~~ B ) ) )  | 
						
						
							| 64 | 
							
								9 63
							 | 
							biimtrid | 
							 |-  ( x e. _om -> ( A ~~ x -> ( B C. A -> -. x ~~ B ) ) )  | 
						
						
							| 65 | 
							
								64
							 | 
							imp31 | 
							 |-  ( ( ( x e. _om /\ A ~~ x ) /\ B C. A ) -> -. x ~~ B )  | 
						
						
							| 66 | 
							
								
							 | 
							entr | 
							 |-  ( ( B ~~ A /\ A ~~ x ) -> B ~~ x )  | 
						
						
							| 67 | 
							
								66
							 | 
							ex | 
							 |-  ( B ~~ A -> ( A ~~ x -> B ~~ x ) )  | 
						
						
							| 68 | 
							
								
							 | 
							ensym | 
							 |-  ( B ~~ x -> x ~~ B )  | 
						
						
							| 69 | 
							
								67 68
							 | 
							syl6com | 
							 |-  ( A ~~ x -> ( B ~~ A -> x ~~ B ) )  | 
						
						
							| 70 | 
							
								69
							 | 
							ad2antlr | 
							 |-  ( ( ( x e. _om /\ A ~~ x ) /\ B C. A ) -> ( B ~~ A -> x ~~ B ) )  | 
						
						
							| 71 | 
							
								65 70
							 | 
							mtod | 
							 |-  ( ( ( x e. _om /\ A ~~ x ) /\ B C. A ) -> -. B ~~ A )  | 
						
						
							| 72 | 
							
								
							 | 
							brsdom | 
							 |-  ( B ~< A <-> ( B ~<_ A /\ -. B ~~ A ) )  | 
						
						
							| 73 | 
							
								8 71 72
							 | 
							sylanbrc | 
							 |-  ( ( ( x e. _om /\ A ~~ x ) /\ B C. A ) -> B ~< A )  | 
						
						
							| 74 | 
							
								73
							 | 
							exp31 | 
							 |-  ( x e. _om -> ( A ~~ x -> ( B C. A -> B ~< A ) ) )  | 
						
						
							| 75 | 
							
								74
							 | 
							rexlimiv | 
							 |-  ( E. x e. _om A ~~ x -> ( B C. A -> B ~< A ) )  | 
						
						
							| 76 | 
							
								1 75
							 | 
							sylbi | 
							 |-  ( A e. Fin -> ( B C. A -> B ~< A ) )  | 
						
						
							| 77 | 
							
								76
							 | 
							imp | 
							 |-  ( ( A e. Fin /\ B C. A ) -> B ~< A )  |