| Step | Hyp | Ref | Expression | 
						
							| 1 |  | opabex3.1 |  |-  A e. _V | 
						
							| 2 |  | opabex3.2 |  |-  ( x e. A -> { y | ph } e. _V ) | 
						
							| 3 |  | 19.42v |  |-  ( E. y ( x e. A /\ ( z = <. x , y >. /\ ph ) ) <-> ( x e. A /\ E. y ( z = <. x , y >. /\ ph ) ) ) | 
						
							| 4 |  | an12 |  |-  ( ( z = <. x , y >. /\ ( x e. A /\ ph ) ) <-> ( x e. A /\ ( z = <. x , y >. /\ ph ) ) ) | 
						
							| 5 | 4 | exbii |  |-  ( E. y ( z = <. x , y >. /\ ( x e. A /\ ph ) ) <-> E. y ( x e. A /\ ( z = <. x , y >. /\ ph ) ) ) | 
						
							| 6 |  | elxp |  |-  ( z e. ( { x } X. { y | ph } ) <-> E. v E. w ( z = <. v , w >. /\ ( v e. { x } /\ w e. { y | ph } ) ) ) | 
						
							| 7 |  | excom |  |-  ( E. v E. w ( z = <. v , w >. /\ ( v e. { x } /\ w e. { y | ph } ) ) <-> E. w E. v ( z = <. v , w >. /\ ( v e. { x } /\ w e. { y | ph } ) ) ) | 
						
							| 8 |  | an12 |  |-  ( ( z = <. v , w >. /\ ( v e. { x } /\ w e. { y | ph } ) ) <-> ( v e. { x } /\ ( z = <. v , w >. /\ w e. { y | ph } ) ) ) | 
						
							| 9 |  | velsn |  |-  ( v e. { x } <-> v = x ) | 
						
							| 10 | 9 | anbi1i |  |-  ( ( v e. { x } /\ ( z = <. v , w >. /\ w e. { y | ph } ) ) <-> ( v = x /\ ( z = <. v , w >. /\ w e. { y | ph } ) ) ) | 
						
							| 11 | 8 10 | bitri |  |-  ( ( z = <. v , w >. /\ ( v e. { x } /\ w e. { y | ph } ) ) <-> ( v = x /\ ( z = <. v , w >. /\ w e. { y | ph } ) ) ) | 
						
							| 12 | 11 | exbii |  |-  ( E. v ( z = <. v , w >. /\ ( v e. { x } /\ w e. { y | ph } ) ) <-> E. v ( v = x /\ ( z = <. v , w >. /\ w e. { y | ph } ) ) ) | 
						
							| 13 |  | opeq1 |  |-  ( v = x -> <. v , w >. = <. x , w >. ) | 
						
							| 14 | 13 | eqeq2d |  |-  ( v = x -> ( z = <. v , w >. <-> z = <. x , w >. ) ) | 
						
							| 15 | 14 | anbi1d |  |-  ( v = x -> ( ( z = <. v , w >. /\ w e. { y | ph } ) <-> ( z = <. x , w >. /\ w e. { y | ph } ) ) ) | 
						
							| 16 | 15 | equsexvw |  |-  ( E. v ( v = x /\ ( z = <. v , w >. /\ w e. { y | ph } ) ) <-> ( z = <. x , w >. /\ w e. { y | ph } ) ) | 
						
							| 17 | 12 16 | bitri |  |-  ( E. v ( z = <. v , w >. /\ ( v e. { x } /\ w e. { y | ph } ) ) <-> ( z = <. x , w >. /\ w e. { y | ph } ) ) | 
						
							| 18 | 17 | exbii |  |-  ( E. w E. v ( z = <. v , w >. /\ ( v e. { x } /\ w e. { y | ph } ) ) <-> E. w ( z = <. x , w >. /\ w e. { y | ph } ) ) | 
						
							| 19 | 7 18 | bitri |  |-  ( E. v E. w ( z = <. v , w >. /\ ( v e. { x } /\ w e. { y | ph } ) ) <-> E. w ( z = <. x , w >. /\ w e. { y | ph } ) ) | 
						
							| 20 |  | nfv |  |-  F/ y z = <. x , w >. | 
						
							| 21 |  | nfsab1 |  |-  F/ y w e. { y | ph } | 
						
							| 22 | 20 21 | nfan |  |-  F/ y ( z = <. x , w >. /\ w e. { y | ph } ) | 
						
							| 23 |  | nfv |  |-  F/ w ( z = <. x , y >. /\ ph ) | 
						
							| 24 |  | opeq2 |  |-  ( w = y -> <. x , w >. = <. x , y >. ) | 
						
							| 25 | 24 | eqeq2d |  |-  ( w = y -> ( z = <. x , w >. <-> z = <. x , y >. ) ) | 
						
							| 26 |  | df-clab |  |-  ( w e. { y | ph } <-> [ w / y ] ph ) | 
						
							| 27 |  | sbequ12 |  |-  ( y = w -> ( ph <-> [ w / y ] ph ) ) | 
						
							| 28 | 27 | equcoms |  |-  ( w = y -> ( ph <-> [ w / y ] ph ) ) | 
						
							| 29 | 26 28 | bitr4id |  |-  ( w = y -> ( w e. { y | ph } <-> ph ) ) | 
						
							| 30 | 25 29 | anbi12d |  |-  ( w = y -> ( ( z = <. x , w >. /\ w e. { y | ph } ) <-> ( z = <. x , y >. /\ ph ) ) ) | 
						
							| 31 | 22 23 30 | cbvexv1 |  |-  ( E. w ( z = <. x , w >. /\ w e. { y | ph } ) <-> E. y ( z = <. x , y >. /\ ph ) ) | 
						
							| 32 | 6 19 31 | 3bitri |  |-  ( z e. ( { x } X. { y | ph } ) <-> E. y ( z = <. x , y >. /\ ph ) ) | 
						
							| 33 | 32 | anbi2i |  |-  ( ( x e. A /\ z e. ( { x } X. { y | ph } ) ) <-> ( x e. A /\ E. y ( z = <. x , y >. /\ ph ) ) ) | 
						
							| 34 | 3 5 33 | 3bitr4ri |  |-  ( ( x e. A /\ z e. ( { x } X. { y | ph } ) ) <-> E. y ( z = <. x , y >. /\ ( x e. A /\ ph ) ) ) | 
						
							| 35 | 34 | exbii |  |-  ( E. x ( x e. A /\ z e. ( { x } X. { y | ph } ) ) <-> E. x E. y ( z = <. x , y >. /\ ( x e. A /\ ph ) ) ) | 
						
							| 36 |  | eliun |  |-  ( z e. U_ x e. A ( { x } X. { y | ph } ) <-> E. x e. A z e. ( { x } X. { y | ph } ) ) | 
						
							| 37 |  | df-rex |  |-  ( E. x e. A z e. ( { x } X. { y | ph } ) <-> E. x ( x e. A /\ z e. ( { x } X. { y | ph } ) ) ) | 
						
							| 38 | 36 37 | bitri |  |-  ( z e. U_ x e. A ( { x } X. { y | ph } ) <-> E. x ( x e. A /\ z e. ( { x } X. { y | ph } ) ) ) | 
						
							| 39 |  | elopab |  |-  ( z e. { <. x , y >. | ( x e. A /\ ph ) } <-> E. x E. y ( z = <. x , y >. /\ ( x e. A /\ ph ) ) ) | 
						
							| 40 | 35 38 39 | 3bitr4i |  |-  ( z e. U_ x e. A ( { x } X. { y | ph } ) <-> z e. { <. x , y >. | ( x e. A /\ ph ) } ) | 
						
							| 41 | 40 | eqriv |  |-  U_ x e. A ( { x } X. { y | ph } ) = { <. x , y >. | ( x e. A /\ ph ) } | 
						
							| 42 |  | vsnex |  |-  { x } e. _V | 
						
							| 43 |  | xpexg |  |-  ( ( { x } e. _V /\ { y | ph } e. _V ) -> ( { x } X. { y | ph } ) e. _V ) | 
						
							| 44 | 42 2 43 | sylancr |  |-  ( x e. A -> ( { x } X. { y | ph } ) e. _V ) | 
						
							| 45 | 44 | rgen |  |-  A. x e. A ( { x } X. { y | ph } ) e. _V | 
						
							| 46 |  | iunexg |  |-  ( ( A e. _V /\ A. x e. A ( { x } X. { y | ph } ) e. _V ) -> U_ x e. A ( { x } X. { y | ph } ) e. _V ) | 
						
							| 47 | 1 45 46 | mp2an |  |-  U_ x e. A ( { x } X. { y | ph } ) e. _V | 
						
							| 48 | 41 47 | eqeltrri |  |-  { <. x , y >. | ( x e. A /\ ph ) } e. _V |