| Step | Hyp | Ref | Expression | 
						
							| 1 |  | df-finxp |  |-  ( U ^^ N ) = { y | ( N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) ) } | 
						
							| 2 | 1 | csbeq2i |  |-  [_ A / x ]_ ( U ^^ N ) = [_ A / x ]_ { y | ( N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) ) } | 
						
							| 3 |  | sbcan |  |-  ( [. A / x ]. ( N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) ) <-> ( [. A / x ]. N e. _om /\ [. A / x ]. (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) ) ) | 
						
							| 4 |  | sbcel1g |  |-  ( A e. V -> ( [. A / x ]. N e. _om <-> [_ A / x ]_ N e. _om ) ) | 
						
							| 5 |  | sbceq2g |  |-  ( A e. V -> ( [. A / x ]. (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) <-> (/) = [_ A / x ]_ ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) ) ) | 
						
							| 6 |  | csbfv12 |  |-  [_ A / x ]_ ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) = ( [_ A / x ]_ rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` [_ A / x ]_ N ) | 
						
							| 7 |  | csbrdgg |  |-  ( A e. V -> [_ A / x ]_ rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) = rec ( [_ A / x ]_ ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , [_ A / x ]_ <. N , y >. ) ) | 
						
							| 8 |  | csbmpo123 |  |-  ( A e. V -> [_ A / x ]_ ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) = ( n e. [_ A / x ]_ _om , z e. [_ A / x ]_ _V |-> [_ A / x ]_ if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) ) | 
						
							| 9 |  | csbconstg |  |-  ( A e. V -> [_ A / x ]_ _om = _om ) | 
						
							| 10 |  | csbconstg |  |-  ( A e. V -> [_ A / x ]_ _V = _V ) | 
						
							| 11 |  | csbif |  |-  [_ A / x ]_ if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) = if ( [. A / x ]. ( n = 1o /\ z e. U ) , [_ A / x ]_ (/) , [_ A / x ]_ if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) | 
						
							| 12 |  | sbcan |  |-  ( [. A / x ]. ( n = 1o /\ z e. U ) <-> ( [. A / x ]. n = 1o /\ [. A / x ]. z e. U ) ) | 
						
							| 13 |  | sbcg |  |-  ( A e. V -> ( [. A / x ]. n = 1o <-> n = 1o ) ) | 
						
							| 14 |  | sbcel12 |  |-  ( [. A / x ]. z e. U <-> [_ A / x ]_ z e. [_ A / x ]_ U ) | 
						
							| 15 |  | csbconstg |  |-  ( A e. V -> [_ A / x ]_ z = z ) | 
						
							| 16 | 15 | eleq1d |  |-  ( A e. V -> ( [_ A / x ]_ z e. [_ A / x ]_ U <-> z e. [_ A / x ]_ U ) ) | 
						
							| 17 | 14 16 | bitrid |  |-  ( A e. V -> ( [. A / x ]. z e. U <-> z e. [_ A / x ]_ U ) ) | 
						
							| 18 | 13 17 | anbi12d |  |-  ( A e. V -> ( ( [. A / x ]. n = 1o /\ [. A / x ]. z e. U ) <-> ( n = 1o /\ z e. [_ A / x ]_ U ) ) ) | 
						
							| 19 | 12 18 | bitrid |  |-  ( A e. V -> ( [. A / x ]. ( n = 1o /\ z e. U ) <-> ( n = 1o /\ z e. [_ A / x ]_ U ) ) ) | 
						
							| 20 |  | csbconstg |  |-  ( A e. V -> [_ A / x ]_ (/) = (/) ) | 
						
							| 21 |  | csbif |  |-  [_ A / x ]_ if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) = if ( [. A / x ]. z e. ( _V X. U ) , [_ A / x ]_ <. U. n , ( 1st ` z ) >. , [_ A / x ]_ <. n , z >. ) | 
						
							| 22 |  | sbcel12 |  |-  ( [. A / x ]. z e. ( _V X. U ) <-> [_ A / x ]_ z e. [_ A / x ]_ ( _V X. U ) ) | 
						
							| 23 |  | csbxp |  |-  [_ A / x ]_ ( _V X. U ) = ( [_ A / x ]_ _V X. [_ A / x ]_ U ) | 
						
							| 24 | 10 | xpeq1d |  |-  ( A e. V -> ( [_ A / x ]_ _V X. [_ A / x ]_ U ) = ( _V X. [_ A / x ]_ U ) ) | 
						
							| 25 | 23 24 | eqtrid |  |-  ( A e. V -> [_ A / x ]_ ( _V X. U ) = ( _V X. [_ A / x ]_ U ) ) | 
						
							| 26 | 15 25 | eleq12d |  |-  ( A e. V -> ( [_ A / x ]_ z e. [_ A / x ]_ ( _V X. U ) <-> z e. ( _V X. [_ A / x ]_ U ) ) ) | 
						
							| 27 | 22 26 | bitrid |  |-  ( A e. V -> ( [. A / x ]. z e. ( _V X. U ) <-> z e. ( _V X. [_ A / x ]_ U ) ) ) | 
						
							| 28 |  | csbconstg |  |-  ( A e. V -> [_ A / x ]_ <. U. n , ( 1st ` z ) >. = <. U. n , ( 1st ` z ) >. ) | 
						
							| 29 |  | csbconstg |  |-  ( A e. V -> [_ A / x ]_ <. n , z >. = <. n , z >. ) | 
						
							| 30 | 27 28 29 | ifbieq12d |  |-  ( A e. V -> if ( [. A / x ]. z e. ( _V X. U ) , [_ A / x ]_ <. U. n , ( 1st ` z ) >. , [_ A / x ]_ <. n , z >. ) = if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) | 
						
							| 31 | 21 30 | eqtrid |  |-  ( A e. V -> [_ A / x ]_ if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) = if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) | 
						
							| 32 | 19 20 31 | ifbieq12d |  |-  ( A e. V -> if ( [. A / x ]. ( n = 1o /\ z e. U ) , [_ A / x ]_ (/) , [_ A / x ]_ if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) = if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) | 
						
							| 33 | 11 32 | eqtrid |  |-  ( A e. V -> [_ A / x ]_ if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) = if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) | 
						
							| 34 | 9 10 33 | mpoeq123dv |  |-  ( A e. V -> ( n e. [_ A / x ]_ _om , z e. [_ A / x ]_ _V |-> [_ A / x ]_ if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) = ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) ) | 
						
							| 35 | 8 34 | eqtrd |  |-  ( A e. V -> [_ A / x ]_ ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) = ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) ) | 
						
							| 36 |  | csbopg |  |-  ( A e. V -> [_ A / x ]_ <. N , y >. = <. [_ A / x ]_ N , [_ A / x ]_ y >. ) | 
						
							| 37 |  | csbconstg |  |-  ( A e. V -> [_ A / x ]_ y = y ) | 
						
							| 38 | 37 | opeq2d |  |-  ( A e. V -> <. [_ A / x ]_ N , [_ A / x ]_ y >. = <. [_ A / x ]_ N , y >. ) | 
						
							| 39 | 36 38 | eqtrd |  |-  ( A e. V -> [_ A / x ]_ <. N , y >. = <. [_ A / x ]_ N , y >. ) | 
						
							| 40 |  | rdgeq12 |  |-  ( ( [_ A / x ]_ ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) = ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) /\ [_ A / x ]_ <. N , y >. = <. [_ A / x ]_ N , y >. ) -> rec ( [_ A / x ]_ ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , [_ A / x ]_ <. N , y >. ) = rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. [_ A / x ]_ N , y >. ) ) | 
						
							| 41 | 35 39 40 | syl2anc |  |-  ( A e. V -> rec ( [_ A / x ]_ ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , [_ A / x ]_ <. N , y >. ) = rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. [_ A / x ]_ N , y >. ) ) | 
						
							| 42 | 7 41 | eqtrd |  |-  ( A e. V -> [_ A / x ]_ rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) = rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. [_ A / x ]_ N , y >. ) ) | 
						
							| 43 | 42 | fveq1d |  |-  ( A e. V -> ( [_ A / x ]_ rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` [_ A / x ]_ N ) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. [_ A / x ]_ N , y >. ) ` [_ A / x ]_ N ) ) | 
						
							| 44 | 6 43 | eqtrid |  |-  ( A e. V -> [_ A / x ]_ ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. [_ A / x ]_ N , y >. ) ` [_ A / x ]_ N ) ) | 
						
							| 45 | 44 | eqeq2d |  |-  ( A e. V -> ( (/) = [_ A / x ]_ ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) <-> (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. [_ A / x ]_ N , y >. ) ` [_ A / x ]_ N ) ) ) | 
						
							| 46 | 5 45 | bitrd |  |-  ( A e. V -> ( [. A / x ]. (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) <-> (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. [_ A / x ]_ N , y >. ) ` [_ A / x ]_ N ) ) ) | 
						
							| 47 | 4 46 | anbi12d |  |-  ( A e. V -> ( ( [. A / x ]. N e. _om /\ [. A / x ]. (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) ) <-> ( [_ A / x ]_ N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. [_ A / x ]_ N , y >. ) ` [_ A / x ]_ N ) ) ) ) | 
						
							| 48 | 3 47 | bitrid |  |-  ( A e. V -> ( [. A / x ]. ( N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) ) <-> ( [_ A / x ]_ N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. [_ A / x ]_ N , y >. ) ` [_ A / x ]_ N ) ) ) ) | 
						
							| 49 | 48 | abbidv |  |-  ( A e. V -> { y | [. A / x ]. ( N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) ) } = { y | ( [_ A / x ]_ N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. [_ A / x ]_ N , y >. ) ` [_ A / x ]_ N ) ) } ) | 
						
							| 50 |  | csbab |  |-  [_ A / x ]_ { y | ( N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) ) } = { y | [. A / x ]. ( N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) ) } | 
						
							| 51 |  | df-finxp |  |-  ( [_ A / x ]_ U ^^ [_ A / x ]_ N ) = { y | ( [_ A / x ]_ N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. [_ A / x ]_ U ) , (/) , if ( z e. ( _V X. [_ A / x ]_ U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. [_ A / x ]_ N , y >. ) ` [_ A / x ]_ N ) ) } | 
						
							| 52 | 49 50 51 | 3eqtr4g |  |-  ( A e. V -> [_ A / x ]_ { y | ( N e. _om /\ (/) = ( rec ( ( n e. _om , z e. _V |-> if ( ( n = 1o /\ z e. U ) , (/) , if ( z e. ( _V X. U ) , <. U. n , ( 1st ` z ) >. , <. n , z >. ) ) ) , <. N , y >. ) ` N ) ) } = ( [_ A / x ]_ U ^^ [_ A / x ]_ N ) ) | 
						
							| 53 | 2 52 | eqtrid |  |-  ( A e. V -> [_ A / x ]_ ( U ^^ N ) = ( [_ A / x ]_ U ^^ [_ A / x ]_ N ) ) |