| Step | Hyp | Ref | Expression | 
						
							| 1 |  | unxpwdom3.av |  |-  ( ph -> A e. V ) | 
						
							| 2 |  | unxpwdom3.bv |  |-  ( ph -> B e. W ) | 
						
							| 3 |  | unxpwdom3.dv |  |-  ( ph -> D e. X ) | 
						
							| 4 |  | unxpwdom3.ov |  |-  ( ( ph /\ a e. C /\ b e. D ) -> ( a .+ b ) e. ( A u. B ) ) | 
						
							| 5 |  | unxpwdom3.lc |  |-  ( ( ( ph /\ a e. C ) /\ ( b e. D /\ c e. D ) ) -> ( ( a .+ b ) = ( a .+ c ) <-> b = c ) ) | 
						
							| 6 |  | unxpwdom3.rc |  |-  ( ( ( ph /\ d e. D ) /\ ( a e. C /\ c e. C ) ) -> ( ( c .+ d ) = ( a .+ d ) <-> c = a ) ) | 
						
							| 7 |  | unxpwdom3.ni |  |-  ( ph -> -. D ~<_ A ) | 
						
							| 8 | 3 2 | xpexd |  |-  ( ph -> ( D X. B ) e. _V ) | 
						
							| 9 |  | simprr |  |-  ( ( ( ph /\ a e. C ) /\ ( d e. D /\ ( a .+ d ) e. B ) ) -> ( a .+ d ) e. B ) | 
						
							| 10 |  | simplr |  |-  ( ( ( ph /\ a e. C ) /\ ( d e. D /\ ( a .+ d ) e. B ) ) -> a e. C ) | 
						
							| 11 | 6 | an4s |  |-  ( ( ( ph /\ a e. C ) /\ ( d e. D /\ c e. C ) ) -> ( ( c .+ d ) = ( a .+ d ) <-> c = a ) ) | 
						
							| 12 | 11 | anassrs |  |-  ( ( ( ( ph /\ a e. C ) /\ d e. D ) /\ c e. C ) -> ( ( c .+ d ) = ( a .+ d ) <-> c = a ) ) | 
						
							| 13 | 12 | adantlrr |  |-  ( ( ( ( ph /\ a e. C ) /\ ( d e. D /\ ( a .+ d ) e. B ) ) /\ c e. C ) -> ( ( c .+ d ) = ( a .+ d ) <-> c = a ) ) | 
						
							| 14 | 10 13 | riota5 |  |-  ( ( ( ph /\ a e. C ) /\ ( d e. D /\ ( a .+ d ) e. B ) ) -> ( iota_ c e. C ( c .+ d ) = ( a .+ d ) ) = a ) | 
						
							| 15 | 14 | eqcomd |  |-  ( ( ( ph /\ a e. C ) /\ ( d e. D /\ ( a .+ d ) e. B ) ) -> a = ( iota_ c e. C ( c .+ d ) = ( a .+ d ) ) ) | 
						
							| 16 |  | eqeq2 |  |-  ( y = ( a .+ d ) -> ( ( c .+ d ) = y <-> ( c .+ d ) = ( a .+ d ) ) ) | 
						
							| 17 | 16 | riotabidv |  |-  ( y = ( a .+ d ) -> ( iota_ c e. C ( c .+ d ) = y ) = ( iota_ c e. C ( c .+ d ) = ( a .+ d ) ) ) | 
						
							| 18 | 17 | rspceeqv |  |-  ( ( ( a .+ d ) e. B /\ a = ( iota_ c e. C ( c .+ d ) = ( a .+ d ) ) ) -> E. y e. B a = ( iota_ c e. C ( c .+ d ) = y ) ) | 
						
							| 19 | 9 15 18 | syl2anc |  |-  ( ( ( ph /\ a e. C ) /\ ( d e. D /\ ( a .+ d ) e. B ) ) -> E. y e. B a = ( iota_ c e. C ( c .+ d ) = y ) ) | 
						
							| 20 | 7 | adantr |  |-  ( ( ph /\ a e. C ) -> -. D ~<_ A ) | 
						
							| 21 | 1 | ad2antrr |  |-  ( ( ( ph /\ a e. C ) /\ A. d e. D -. ( a .+ d ) e. B ) -> A e. V ) | 
						
							| 22 |  | oveq2 |  |-  ( d = b -> ( a .+ d ) = ( a .+ b ) ) | 
						
							| 23 | 22 | eleq1d |  |-  ( d = b -> ( ( a .+ d ) e. B <-> ( a .+ b ) e. B ) ) | 
						
							| 24 | 23 | notbid |  |-  ( d = b -> ( -. ( a .+ d ) e. B <-> -. ( a .+ b ) e. B ) ) | 
						
							| 25 | 24 | rspcv |  |-  ( b e. D -> ( A. d e. D -. ( a .+ d ) e. B -> -. ( a .+ b ) e. B ) ) | 
						
							| 26 | 25 | adantl |  |-  ( ( ( ph /\ a e. C ) /\ b e. D ) -> ( A. d e. D -. ( a .+ d ) e. B -> -. ( a .+ b ) e. B ) ) | 
						
							| 27 | 4 | 3expa |  |-  ( ( ( ph /\ a e. C ) /\ b e. D ) -> ( a .+ b ) e. ( A u. B ) ) | 
						
							| 28 |  | elun |  |-  ( ( a .+ b ) e. ( A u. B ) <-> ( ( a .+ b ) e. A \/ ( a .+ b ) e. B ) ) | 
						
							| 29 | 27 28 | sylib |  |-  ( ( ( ph /\ a e. C ) /\ b e. D ) -> ( ( a .+ b ) e. A \/ ( a .+ b ) e. B ) ) | 
						
							| 30 | 29 | orcomd |  |-  ( ( ( ph /\ a e. C ) /\ b e. D ) -> ( ( a .+ b ) e. B \/ ( a .+ b ) e. A ) ) | 
						
							| 31 | 30 | ord |  |-  ( ( ( ph /\ a e. C ) /\ b e. D ) -> ( -. ( a .+ b ) e. B -> ( a .+ b ) e. A ) ) | 
						
							| 32 | 26 31 | syld |  |-  ( ( ( ph /\ a e. C ) /\ b e. D ) -> ( A. d e. D -. ( a .+ d ) e. B -> ( a .+ b ) e. A ) ) | 
						
							| 33 | 32 | impancom |  |-  ( ( ( ph /\ a e. C ) /\ A. d e. D -. ( a .+ d ) e. B ) -> ( b e. D -> ( a .+ b ) e. A ) ) | 
						
							| 34 | 5 | ex |  |-  ( ( ph /\ a e. C ) -> ( ( b e. D /\ c e. D ) -> ( ( a .+ b ) = ( a .+ c ) <-> b = c ) ) ) | 
						
							| 35 | 34 | adantr |  |-  ( ( ( ph /\ a e. C ) /\ A. d e. D -. ( a .+ d ) e. B ) -> ( ( b e. D /\ c e. D ) -> ( ( a .+ b ) = ( a .+ c ) <-> b = c ) ) ) | 
						
							| 36 | 33 35 | dom2d |  |-  ( ( ( ph /\ a e. C ) /\ A. d e. D -. ( a .+ d ) e. B ) -> ( A e. V -> D ~<_ A ) ) | 
						
							| 37 | 21 36 | mpd |  |-  ( ( ( ph /\ a e. C ) /\ A. d e. D -. ( a .+ d ) e. B ) -> D ~<_ A ) | 
						
							| 38 | 20 37 | mtand |  |-  ( ( ph /\ a e. C ) -> -. A. d e. D -. ( a .+ d ) e. B ) | 
						
							| 39 |  | dfrex2 |  |-  ( E. d e. D ( a .+ d ) e. B <-> -. A. d e. D -. ( a .+ d ) e. B ) | 
						
							| 40 | 38 39 | sylibr |  |-  ( ( ph /\ a e. C ) -> E. d e. D ( a .+ d ) e. B ) | 
						
							| 41 | 19 40 | reximddv |  |-  ( ( ph /\ a e. C ) -> E. d e. D E. y e. B a = ( iota_ c e. C ( c .+ d ) = y ) ) | 
						
							| 42 |  | vex |  |-  d e. _V | 
						
							| 43 |  | vex |  |-  y e. _V | 
						
							| 44 | 42 43 | op1std |  |-  ( x = <. d , y >. -> ( 1st ` x ) = d ) | 
						
							| 45 | 44 | oveq2d |  |-  ( x = <. d , y >. -> ( c .+ ( 1st ` x ) ) = ( c .+ d ) ) | 
						
							| 46 | 42 43 | op2ndd |  |-  ( x = <. d , y >. -> ( 2nd ` x ) = y ) | 
						
							| 47 | 45 46 | eqeq12d |  |-  ( x = <. d , y >. -> ( ( c .+ ( 1st ` x ) ) = ( 2nd ` x ) <-> ( c .+ d ) = y ) ) | 
						
							| 48 | 47 | riotabidv |  |-  ( x = <. d , y >. -> ( iota_ c e. C ( c .+ ( 1st ` x ) ) = ( 2nd ` x ) ) = ( iota_ c e. C ( c .+ d ) = y ) ) | 
						
							| 49 | 48 | eqeq2d |  |-  ( x = <. d , y >. -> ( a = ( iota_ c e. C ( c .+ ( 1st ` x ) ) = ( 2nd ` x ) ) <-> a = ( iota_ c e. C ( c .+ d ) = y ) ) ) | 
						
							| 50 | 49 | rexxp |  |-  ( E. x e. ( D X. B ) a = ( iota_ c e. C ( c .+ ( 1st ` x ) ) = ( 2nd ` x ) ) <-> E. d e. D E. y e. B a = ( iota_ c e. C ( c .+ d ) = y ) ) | 
						
							| 51 | 41 50 | sylibr |  |-  ( ( ph /\ a e. C ) -> E. x e. ( D X. B ) a = ( iota_ c e. C ( c .+ ( 1st ` x ) ) = ( 2nd ` x ) ) ) | 
						
							| 52 | 8 51 | wdomd |  |-  ( ph -> C ~<_* ( D X. B ) ) |