| Step | Hyp | Ref | Expression | 
						
							| 1 |  | breq1 |  |-  ( x = (/) -> ( x ~~ z <-> (/) ~~ z ) ) | 
						
							| 2 |  | eqeq1 |  |-  ( x = (/) -> ( x = z <-> (/) = z ) ) | 
						
							| 3 | 1 2 | imbi12d |  |-  ( x = (/) -> ( ( x ~~ z -> x = z ) <-> ( (/) ~~ z -> (/) = z ) ) ) | 
						
							| 4 | 3 | ralbidv |  |-  ( x = (/) -> ( A. z e. _om ( x ~~ z -> x = z ) <-> A. z e. _om ( (/) ~~ z -> (/) = z ) ) ) | 
						
							| 5 |  | breq1 |  |-  ( x = y -> ( x ~~ z <-> y ~~ z ) ) | 
						
							| 6 |  | eqeq1 |  |-  ( x = y -> ( x = z <-> y = z ) ) | 
						
							| 7 | 5 6 | imbi12d |  |-  ( x = y -> ( ( x ~~ z -> x = z ) <-> ( y ~~ z -> y = z ) ) ) | 
						
							| 8 | 7 | ralbidv |  |-  ( x = y -> ( A. z e. _om ( x ~~ z -> x = z ) <-> A. z e. _om ( y ~~ z -> y = z ) ) ) | 
						
							| 9 |  | breq1 |  |-  ( x = suc y -> ( x ~~ z <-> suc y ~~ z ) ) | 
						
							| 10 |  | eqeq1 |  |-  ( x = suc y -> ( x = z <-> suc y = z ) ) | 
						
							| 11 | 9 10 | imbi12d |  |-  ( x = suc y -> ( ( x ~~ z -> x = z ) <-> ( suc y ~~ z -> suc y = z ) ) ) | 
						
							| 12 | 11 | ralbidv |  |-  ( x = suc y -> ( A. z e. _om ( x ~~ z -> x = z ) <-> A. z e. _om ( suc y ~~ z -> suc y = z ) ) ) | 
						
							| 13 |  | breq1 |  |-  ( x = A -> ( x ~~ z <-> A ~~ z ) ) | 
						
							| 14 |  | eqeq1 |  |-  ( x = A -> ( x = z <-> A = z ) ) | 
						
							| 15 | 13 14 | imbi12d |  |-  ( x = A -> ( ( x ~~ z -> x = z ) <-> ( A ~~ z -> A = z ) ) ) | 
						
							| 16 | 15 | ralbidv |  |-  ( x = A -> ( A. z e. _om ( x ~~ z -> x = z ) <-> A. z e. _om ( A ~~ z -> A = z ) ) ) | 
						
							| 17 |  | ensym |  |-  ( (/) ~~ z -> z ~~ (/) ) | 
						
							| 18 |  | en0 |  |-  ( z ~~ (/) <-> z = (/) ) | 
						
							| 19 |  | eqcom |  |-  ( z = (/) <-> (/) = z ) | 
						
							| 20 | 18 19 | bitri |  |-  ( z ~~ (/) <-> (/) = z ) | 
						
							| 21 | 17 20 | sylib |  |-  ( (/) ~~ z -> (/) = z ) | 
						
							| 22 | 21 | rgenw |  |-  A. z e. _om ( (/) ~~ z -> (/) = z ) | 
						
							| 23 |  | nn0suc |  |-  ( w e. _om -> ( w = (/) \/ E. z e. _om w = suc z ) ) | 
						
							| 24 |  | en0 |  |-  ( suc y ~~ (/) <-> suc y = (/) ) | 
						
							| 25 |  | breq2 |  |-  ( w = (/) -> ( suc y ~~ w <-> suc y ~~ (/) ) ) | 
						
							| 26 |  | eqeq2 |  |-  ( w = (/) -> ( suc y = w <-> suc y = (/) ) ) | 
						
							| 27 | 25 26 | bibi12d |  |-  ( w = (/) -> ( ( suc y ~~ w <-> suc y = w ) <-> ( suc y ~~ (/) <-> suc y = (/) ) ) ) | 
						
							| 28 | 24 27 | mpbiri |  |-  ( w = (/) -> ( suc y ~~ w <-> suc y = w ) ) | 
						
							| 29 | 28 | biimpd |  |-  ( w = (/) -> ( suc y ~~ w -> suc y = w ) ) | 
						
							| 30 | 29 | a1i |  |-  ( ( y e. _om /\ A. z e. _om ( y ~~ z -> y = z ) ) -> ( w = (/) -> ( suc y ~~ w -> suc y = w ) ) ) | 
						
							| 31 |  | nfv |  |-  F/ z y e. _om | 
						
							| 32 |  | nfra1 |  |-  F/ z A. z e. _om ( y ~~ z -> y = z ) | 
						
							| 33 | 31 32 | nfan |  |-  F/ z ( y e. _om /\ A. z e. _om ( y ~~ z -> y = z ) ) | 
						
							| 34 |  | nfv |  |-  F/ z ( suc y ~~ w -> suc y = w ) | 
						
							| 35 |  | vex |  |-  y e. _V | 
						
							| 36 |  | vex |  |-  z e. _V | 
						
							| 37 | 35 36 | phplem4OLD |  |-  ( ( y e. _om /\ z e. _om ) -> ( suc y ~~ suc z -> y ~~ z ) ) | 
						
							| 38 | 37 | imim1d |  |-  ( ( y e. _om /\ z e. _om ) -> ( ( y ~~ z -> y = z ) -> ( suc y ~~ suc z -> y = z ) ) ) | 
						
							| 39 | 38 | ex |  |-  ( y e. _om -> ( z e. _om -> ( ( y ~~ z -> y = z ) -> ( suc y ~~ suc z -> y = z ) ) ) ) | 
						
							| 40 | 39 | a2d |  |-  ( y e. _om -> ( ( z e. _om -> ( y ~~ z -> y = z ) ) -> ( z e. _om -> ( suc y ~~ suc z -> y = z ) ) ) ) | 
						
							| 41 |  | rsp |  |-  ( A. z e. _om ( y ~~ z -> y = z ) -> ( z e. _om -> ( y ~~ z -> y = z ) ) ) | 
						
							| 42 | 40 41 | impel |  |-  ( ( y e. _om /\ A. z e. _om ( y ~~ z -> y = z ) ) -> ( z e. _om -> ( suc y ~~ suc z -> y = z ) ) ) | 
						
							| 43 |  | suceq |  |-  ( y = z -> suc y = suc z ) | 
						
							| 44 | 42 43 | syl8 |  |-  ( ( y e. _om /\ A. z e. _om ( y ~~ z -> y = z ) ) -> ( z e. _om -> ( suc y ~~ suc z -> suc y = suc z ) ) ) | 
						
							| 45 |  | breq2 |  |-  ( w = suc z -> ( suc y ~~ w <-> suc y ~~ suc z ) ) | 
						
							| 46 |  | eqeq2 |  |-  ( w = suc z -> ( suc y = w <-> suc y = suc z ) ) | 
						
							| 47 | 45 46 | imbi12d |  |-  ( w = suc z -> ( ( suc y ~~ w -> suc y = w ) <-> ( suc y ~~ suc z -> suc y = suc z ) ) ) | 
						
							| 48 | 47 | biimprcd |  |-  ( ( suc y ~~ suc z -> suc y = suc z ) -> ( w = suc z -> ( suc y ~~ w -> suc y = w ) ) ) | 
						
							| 49 | 44 48 | syl6 |  |-  ( ( y e. _om /\ A. z e. _om ( y ~~ z -> y = z ) ) -> ( z e. _om -> ( w = suc z -> ( suc y ~~ w -> suc y = w ) ) ) ) | 
						
							| 50 | 33 34 49 | rexlimd |  |-  ( ( y e. _om /\ A. z e. _om ( y ~~ z -> y = z ) ) -> ( E. z e. _om w = suc z -> ( suc y ~~ w -> suc y = w ) ) ) | 
						
							| 51 | 30 50 | jaod |  |-  ( ( y e. _om /\ A. z e. _om ( y ~~ z -> y = z ) ) -> ( ( w = (/) \/ E. z e. _om w = suc z ) -> ( suc y ~~ w -> suc y = w ) ) ) | 
						
							| 52 | 51 | ex |  |-  ( y e. _om -> ( A. z e. _om ( y ~~ z -> y = z ) -> ( ( w = (/) \/ E. z e. _om w = suc z ) -> ( suc y ~~ w -> suc y = w ) ) ) ) | 
						
							| 53 | 23 52 | syl7 |  |-  ( y e. _om -> ( A. z e. _om ( y ~~ z -> y = z ) -> ( w e. _om -> ( suc y ~~ w -> suc y = w ) ) ) ) | 
						
							| 54 | 53 | ralrimdv |  |-  ( y e. _om -> ( A. z e. _om ( y ~~ z -> y = z ) -> A. w e. _om ( suc y ~~ w -> suc y = w ) ) ) | 
						
							| 55 |  | breq2 |  |-  ( w = z -> ( suc y ~~ w <-> suc y ~~ z ) ) | 
						
							| 56 |  | eqeq2 |  |-  ( w = z -> ( suc y = w <-> suc y = z ) ) | 
						
							| 57 | 55 56 | imbi12d |  |-  ( w = z -> ( ( suc y ~~ w -> suc y = w ) <-> ( suc y ~~ z -> suc y = z ) ) ) | 
						
							| 58 | 57 | cbvralvw |  |-  ( A. w e. _om ( suc y ~~ w -> suc y = w ) <-> A. z e. _om ( suc y ~~ z -> suc y = z ) ) | 
						
							| 59 | 54 58 | imbitrdi |  |-  ( y e. _om -> ( A. z e. _om ( y ~~ z -> y = z ) -> A. z e. _om ( suc y ~~ z -> suc y = z ) ) ) | 
						
							| 60 | 4 8 12 16 22 59 | finds |  |-  ( A e. _om -> A. z e. _om ( A ~~ z -> A = z ) ) | 
						
							| 61 |  | breq2 |  |-  ( z = B -> ( A ~~ z <-> A ~~ B ) ) | 
						
							| 62 |  | eqeq2 |  |-  ( z = B -> ( A = z <-> A = B ) ) | 
						
							| 63 | 61 62 | imbi12d |  |-  ( z = B -> ( ( A ~~ z -> A = z ) <-> ( A ~~ B -> A = B ) ) ) | 
						
							| 64 | 63 | rspcv |  |-  ( B e. _om -> ( A. z e. _om ( A ~~ z -> A = z ) -> ( A ~~ B -> A = B ) ) ) | 
						
							| 65 | 60 64 | mpan9 |  |-  ( ( A e. _om /\ B e. _om ) -> ( A ~~ B -> A = B ) ) | 
						
							| 66 |  | eqeng |  |-  ( A e. _om -> ( A = B -> A ~~ B ) ) | 
						
							| 67 | 66 | adantr |  |-  ( ( A e. _om /\ B e. _om ) -> ( A = B -> A ~~ B ) ) | 
						
							| 68 | 65 67 | impbid |  |-  ( ( A e. _om /\ B e. _om ) -> ( A ~~ B <-> A = B ) ) |