| Step | Hyp | Ref | Expression | 
						
							| 1 |  | reuprg.1 |  |-  ( x = A -> ( ph <-> ps ) ) | 
						
							| 2 |  | reuprg.2 |  |-  ( x = B -> ( ph <-> ch ) ) | 
						
							| 3 |  | nfsbc1v |  |-  F/ x [. c / x ]. ph | 
						
							| 4 |  | nfsbc1v |  |-  F/ x [. w / x ]. ph | 
						
							| 5 |  | sbceq1a |  |-  ( x = w -> ( ph <-> [. w / x ]. ph ) ) | 
						
							| 6 |  | dfsbcq |  |-  ( w = c -> ( [. w / x ]. ph <-> [. c / x ]. ph ) ) | 
						
							| 7 | 3 4 5 6 | reu8nf |  |-  ( E! x e. { A , B } ph <-> E. x e. { A , B } ( ph /\ A. c e. { A , B } ( [. c / x ]. ph -> x = c ) ) ) | 
						
							| 8 |  | nfv |  |-  F/ x ps | 
						
							| 9 |  | nfcv |  |-  F/_ x { A , B } | 
						
							| 10 |  | nfv |  |-  F/ x A = c | 
						
							| 11 | 3 10 | nfim |  |-  F/ x ( [. c / x ]. ph -> A = c ) | 
						
							| 12 | 9 11 | nfralw |  |-  F/ x A. c e. { A , B } ( [. c / x ]. ph -> A = c ) | 
						
							| 13 | 8 12 | nfan |  |-  F/ x ( ps /\ A. c e. { A , B } ( [. c / x ]. ph -> A = c ) ) | 
						
							| 14 |  | nfv |  |-  F/ x ch | 
						
							| 15 |  | nfv |  |-  F/ x B = c | 
						
							| 16 | 3 15 | nfim |  |-  F/ x ( [. c / x ]. ph -> B = c ) | 
						
							| 17 | 9 16 | nfralw |  |-  F/ x A. c e. { A , B } ( [. c / x ]. ph -> B = c ) | 
						
							| 18 | 14 17 | nfan |  |-  F/ x ( ch /\ A. c e. { A , B } ( [. c / x ]. ph -> B = c ) ) | 
						
							| 19 |  | eqeq1 |  |-  ( x = A -> ( x = c <-> A = c ) ) | 
						
							| 20 | 19 | imbi2d |  |-  ( x = A -> ( ( [. c / x ]. ph -> x = c ) <-> ( [. c / x ]. ph -> A = c ) ) ) | 
						
							| 21 | 20 | ralbidv |  |-  ( x = A -> ( A. c e. { A , B } ( [. c / x ]. ph -> x = c ) <-> A. c e. { A , B } ( [. c / x ]. ph -> A = c ) ) ) | 
						
							| 22 | 1 21 | anbi12d |  |-  ( x = A -> ( ( ph /\ A. c e. { A , B } ( [. c / x ]. ph -> x = c ) ) <-> ( ps /\ A. c e. { A , B } ( [. c / x ]. ph -> A = c ) ) ) ) | 
						
							| 23 |  | eqeq1 |  |-  ( x = B -> ( x = c <-> B = c ) ) | 
						
							| 24 | 23 | imbi2d |  |-  ( x = B -> ( ( [. c / x ]. ph -> x = c ) <-> ( [. c / x ]. ph -> B = c ) ) ) | 
						
							| 25 | 24 | ralbidv |  |-  ( x = B -> ( A. c e. { A , B } ( [. c / x ]. ph -> x = c ) <-> A. c e. { A , B } ( [. c / x ]. ph -> B = c ) ) ) | 
						
							| 26 | 2 25 | anbi12d |  |-  ( x = B -> ( ( ph /\ A. c e. { A , B } ( [. c / x ]. ph -> x = c ) ) <-> ( ch /\ A. c e. { A , B } ( [. c / x ]. ph -> B = c ) ) ) ) | 
						
							| 27 | 13 18 22 26 | rexprgf |  |-  ( ( A e. V /\ B e. W ) -> ( E. x e. { A , B } ( ph /\ A. c e. { A , B } ( [. c / x ]. ph -> x = c ) ) <-> ( ( ps /\ A. c e. { A , B } ( [. c / x ]. ph -> A = c ) ) \/ ( ch /\ A. c e. { A , B } ( [. c / x ]. ph -> B = c ) ) ) ) ) | 
						
							| 28 |  | dfsbcq |  |-  ( c = A -> ( [. c / x ]. ph <-> [. A / x ]. ph ) ) | 
						
							| 29 |  | eqeq2 |  |-  ( c = A -> ( A = c <-> A = A ) ) | 
						
							| 30 | 28 29 | imbi12d |  |-  ( c = A -> ( ( [. c / x ]. ph -> A = c ) <-> ( [. A / x ]. ph -> A = A ) ) ) | 
						
							| 31 |  | dfsbcq |  |-  ( c = B -> ( [. c / x ]. ph <-> [. B / x ]. ph ) ) | 
						
							| 32 |  | eqeq2 |  |-  ( c = B -> ( A = c <-> A = B ) ) | 
						
							| 33 | 31 32 | imbi12d |  |-  ( c = B -> ( ( [. c / x ]. ph -> A = c ) <-> ( [. B / x ]. ph -> A = B ) ) ) | 
						
							| 34 | 30 33 | ralprg |  |-  ( ( A e. V /\ B e. W ) -> ( A. c e. { A , B } ( [. c / x ]. ph -> A = c ) <-> ( ( [. A / x ]. ph -> A = A ) /\ ( [. B / x ]. ph -> A = B ) ) ) ) | 
						
							| 35 |  | eqidd |  |-  ( [. A / x ]. ph -> A = A ) | 
						
							| 36 | 35 | biantrur |  |-  ( ( [. B / x ]. ph -> A = B ) <-> ( ( [. A / x ]. ph -> A = A ) /\ ( [. B / x ]. ph -> A = B ) ) ) | 
						
							| 37 | 2 | sbcieg |  |-  ( B e. W -> ( [. B / x ]. ph <-> ch ) ) | 
						
							| 38 | 37 | adantl |  |-  ( ( A e. V /\ B e. W ) -> ( [. B / x ]. ph <-> ch ) ) | 
						
							| 39 | 38 | imbi1d |  |-  ( ( A e. V /\ B e. W ) -> ( ( [. B / x ]. ph -> A = B ) <-> ( ch -> A = B ) ) ) | 
						
							| 40 | 36 39 | bitr3id |  |-  ( ( A e. V /\ B e. W ) -> ( ( ( [. A / x ]. ph -> A = A ) /\ ( [. B / x ]. ph -> A = B ) ) <-> ( ch -> A = B ) ) ) | 
						
							| 41 | 34 40 | bitrd |  |-  ( ( A e. V /\ B e. W ) -> ( A. c e. { A , B } ( [. c / x ]. ph -> A = c ) <-> ( ch -> A = B ) ) ) | 
						
							| 42 | 41 | anbi2d |  |-  ( ( A e. V /\ B e. W ) -> ( ( ps /\ A. c e. { A , B } ( [. c / x ]. ph -> A = c ) ) <-> ( ps /\ ( ch -> A = B ) ) ) ) | 
						
							| 43 |  | eqeq2 |  |-  ( c = A -> ( B = c <-> B = A ) ) | 
						
							| 44 | 28 43 | imbi12d |  |-  ( c = A -> ( ( [. c / x ]. ph -> B = c ) <-> ( [. A / x ]. ph -> B = A ) ) ) | 
						
							| 45 |  | eqeq2 |  |-  ( c = B -> ( B = c <-> B = B ) ) | 
						
							| 46 | 31 45 | imbi12d |  |-  ( c = B -> ( ( [. c / x ]. ph -> B = c ) <-> ( [. B / x ]. ph -> B = B ) ) ) | 
						
							| 47 | 44 46 | ralprg |  |-  ( ( A e. V /\ B e. W ) -> ( A. c e. { A , B } ( [. c / x ]. ph -> B = c ) <-> ( ( [. A / x ]. ph -> B = A ) /\ ( [. B / x ]. ph -> B = B ) ) ) ) | 
						
							| 48 |  | eqidd |  |-  ( [. B / x ]. ph -> B = B ) | 
						
							| 49 | 48 | biantru |  |-  ( ( [. A / x ]. ph -> B = A ) <-> ( ( [. A / x ]. ph -> B = A ) /\ ( [. B / x ]. ph -> B = B ) ) ) | 
						
							| 50 | 1 | sbcieg |  |-  ( A e. V -> ( [. A / x ]. ph <-> ps ) ) | 
						
							| 51 | 50 | adantr |  |-  ( ( A e. V /\ B e. W ) -> ( [. A / x ]. ph <-> ps ) ) | 
						
							| 52 | 51 | imbi1d |  |-  ( ( A e. V /\ B e. W ) -> ( ( [. A / x ]. ph -> B = A ) <-> ( ps -> B = A ) ) ) | 
						
							| 53 | 49 52 | bitr3id |  |-  ( ( A e. V /\ B e. W ) -> ( ( ( [. A / x ]. ph -> B = A ) /\ ( [. B / x ]. ph -> B = B ) ) <-> ( ps -> B = A ) ) ) | 
						
							| 54 | 47 53 | bitrd |  |-  ( ( A e. V /\ B e. W ) -> ( A. c e. { A , B } ( [. c / x ]. ph -> B = c ) <-> ( ps -> B = A ) ) ) | 
						
							| 55 | 54 | anbi2d |  |-  ( ( A e. V /\ B e. W ) -> ( ( ch /\ A. c e. { A , B } ( [. c / x ]. ph -> B = c ) ) <-> ( ch /\ ( ps -> B = A ) ) ) ) | 
						
							| 56 |  | eqcom |  |-  ( B = A <-> A = B ) | 
						
							| 57 | 56 | imbi2i |  |-  ( ( ps -> B = A ) <-> ( ps -> A = B ) ) | 
						
							| 58 | 57 | anbi2i |  |-  ( ( ch /\ ( ps -> B = A ) ) <-> ( ch /\ ( ps -> A = B ) ) ) | 
						
							| 59 | 55 58 | bitrdi |  |-  ( ( A e. V /\ B e. W ) -> ( ( ch /\ A. c e. { A , B } ( [. c / x ]. ph -> B = c ) ) <-> ( ch /\ ( ps -> A = B ) ) ) ) | 
						
							| 60 | 42 59 | orbi12d |  |-  ( ( A e. V /\ B e. W ) -> ( ( ( ps /\ A. c e. { A , B } ( [. c / x ]. ph -> A = c ) ) \/ ( ch /\ A. c e. { A , B } ( [. c / x ]. ph -> B = c ) ) ) <-> ( ( ps /\ ( ch -> A = B ) ) \/ ( ch /\ ( ps -> A = B ) ) ) ) ) | 
						
							| 61 | 27 60 | bitrd |  |-  ( ( A e. V /\ B e. W ) -> ( E. x e. { A , B } ( ph /\ A. c e. { A , B } ( [. c / x ]. ph -> x = c ) ) <-> ( ( ps /\ ( ch -> A = B ) ) \/ ( ch /\ ( ps -> A = B ) ) ) ) ) | 
						
							| 62 | 7 61 | bitrid |  |-  ( ( A e. V /\ B e. W ) -> ( E! x e. { A , B } ph <-> ( ( ps /\ ( ch -> A = B ) ) \/ ( ch /\ ( ps -> A = B ) ) ) ) ) |