| Step | Hyp | Ref | Expression | 
						
							| 1 |  | estrcval.c |  |-  C = ( ExtStrCat ` U ) | 
						
							| 2 |  | estrcval.u |  |-  ( ph -> U e. V ) | 
						
							| 3 |  | estrcval.h |  |-  ( ph -> H = ( x e. U , y e. U |-> ( ( Base ` y ) ^m ( Base ` x ) ) ) ) | 
						
							| 4 |  | estrcval.o |  |-  ( ph -> .x. = ( v e. ( U X. U ) , z e. U |-> ( g e. ( ( Base ` z ) ^m ( Base ` ( 2nd ` v ) ) ) , f e. ( ( Base ` ( 2nd ` v ) ) ^m ( Base ` ( 1st ` v ) ) ) |-> ( g o. f ) ) ) ) | 
						
							| 5 |  | df-estrc |  |-  ExtStrCat = ( u e. _V |-> { <. ( Base ` ndx ) , u >. , <. ( Hom ` ndx ) , ( x e. u , y e. u |-> ( ( Base ` y ) ^m ( Base ` x ) ) ) >. , <. ( comp ` ndx ) , ( v e. ( u X. u ) , z e. u |-> ( g e. ( ( Base ` z ) ^m ( Base ` ( 2nd ` v ) ) ) , f e. ( ( Base ` ( 2nd ` v ) ) ^m ( Base ` ( 1st ` v ) ) ) |-> ( g o. f ) ) ) >. } ) | 
						
							| 6 |  | simpr |  |-  ( ( ph /\ u = U ) -> u = U ) | 
						
							| 7 | 6 | opeq2d |  |-  ( ( ph /\ u = U ) -> <. ( Base ` ndx ) , u >. = <. ( Base ` ndx ) , U >. ) | 
						
							| 8 |  | eqidd |  |-  ( ( ph /\ u = U ) -> ( ( Base ` y ) ^m ( Base ` x ) ) = ( ( Base ` y ) ^m ( Base ` x ) ) ) | 
						
							| 9 | 6 6 8 | mpoeq123dv |  |-  ( ( ph /\ u = U ) -> ( x e. u , y e. u |-> ( ( Base ` y ) ^m ( Base ` x ) ) ) = ( x e. U , y e. U |-> ( ( Base ` y ) ^m ( Base ` x ) ) ) ) | 
						
							| 10 | 3 | adantr |  |-  ( ( ph /\ u = U ) -> H = ( x e. U , y e. U |-> ( ( Base ` y ) ^m ( Base ` x ) ) ) ) | 
						
							| 11 | 9 10 | eqtr4d |  |-  ( ( ph /\ u = U ) -> ( x e. u , y e. u |-> ( ( Base ` y ) ^m ( Base ` x ) ) ) = H ) | 
						
							| 12 | 11 | opeq2d |  |-  ( ( ph /\ u = U ) -> <. ( Hom ` ndx ) , ( x e. u , y e. u |-> ( ( Base ` y ) ^m ( Base ` x ) ) ) >. = <. ( Hom ` ndx ) , H >. ) | 
						
							| 13 | 6 | sqxpeqd |  |-  ( ( ph /\ u = U ) -> ( u X. u ) = ( U X. U ) ) | 
						
							| 14 |  | eqidd |  |-  ( ( ph /\ u = U ) -> ( g e. ( ( Base ` z ) ^m ( Base ` ( 2nd ` v ) ) ) , f e. ( ( Base ` ( 2nd ` v ) ) ^m ( Base ` ( 1st ` v ) ) ) |-> ( g o. f ) ) = ( g e. ( ( Base ` z ) ^m ( Base ` ( 2nd ` v ) ) ) , f e. ( ( Base ` ( 2nd ` v ) ) ^m ( Base ` ( 1st ` v ) ) ) |-> ( g o. f ) ) ) | 
						
							| 15 | 13 6 14 | mpoeq123dv |  |-  ( ( ph /\ u = U ) -> ( v e. ( u X. u ) , z e. u |-> ( g e. ( ( Base ` z ) ^m ( Base ` ( 2nd ` v ) ) ) , f e. ( ( Base ` ( 2nd ` v ) ) ^m ( Base ` ( 1st ` v ) ) ) |-> ( g o. f ) ) ) = ( v e. ( U X. U ) , z e. U |-> ( g e. ( ( Base ` z ) ^m ( Base ` ( 2nd ` v ) ) ) , f e. ( ( Base ` ( 2nd ` v ) ) ^m ( Base ` ( 1st ` v ) ) ) |-> ( g o. f ) ) ) ) | 
						
							| 16 | 4 | adantr |  |-  ( ( ph /\ u = U ) -> .x. = ( v e. ( U X. U ) , z e. U |-> ( g e. ( ( Base ` z ) ^m ( Base ` ( 2nd ` v ) ) ) , f e. ( ( Base ` ( 2nd ` v ) ) ^m ( Base ` ( 1st ` v ) ) ) |-> ( g o. f ) ) ) ) | 
						
							| 17 | 15 16 | eqtr4d |  |-  ( ( ph /\ u = U ) -> ( v e. ( u X. u ) , z e. u |-> ( g e. ( ( Base ` z ) ^m ( Base ` ( 2nd ` v ) ) ) , f e. ( ( Base ` ( 2nd ` v ) ) ^m ( Base ` ( 1st ` v ) ) ) |-> ( g o. f ) ) ) = .x. ) | 
						
							| 18 | 17 | opeq2d |  |-  ( ( ph /\ u = U ) -> <. ( comp ` ndx ) , ( v e. ( u X. u ) , z e. u |-> ( g e. ( ( Base ` z ) ^m ( Base ` ( 2nd ` v ) ) ) , f e. ( ( Base ` ( 2nd ` v ) ) ^m ( Base ` ( 1st ` v ) ) ) |-> ( g o. f ) ) ) >. = <. ( comp ` ndx ) , .x. >. ) | 
						
							| 19 | 7 12 18 | tpeq123d |  |-  ( ( ph /\ u = U ) -> { <. ( Base ` ndx ) , u >. , <. ( Hom ` ndx ) , ( x e. u , y e. u |-> ( ( Base ` y ) ^m ( Base ` x ) ) ) >. , <. ( comp ` ndx ) , ( v e. ( u X. u ) , z e. u |-> ( g e. ( ( Base ` z ) ^m ( Base ` ( 2nd ` v ) ) ) , f e. ( ( Base ` ( 2nd ` v ) ) ^m ( Base ` ( 1st ` v ) ) ) |-> ( g o. f ) ) ) >. } = { <. ( Base ` ndx ) , U >. , <. ( Hom ` ndx ) , H >. , <. ( comp ` ndx ) , .x. >. } ) | 
						
							| 20 | 2 | elexd |  |-  ( ph -> U e. _V ) | 
						
							| 21 |  | tpex |  |-  { <. ( Base ` ndx ) , U >. , <. ( Hom ` ndx ) , H >. , <. ( comp ` ndx ) , .x. >. } e. _V | 
						
							| 22 | 21 | a1i |  |-  ( ph -> { <. ( Base ` ndx ) , U >. , <. ( Hom ` ndx ) , H >. , <. ( comp ` ndx ) , .x. >. } e. _V ) | 
						
							| 23 | 5 19 20 22 | fvmptd2 |  |-  ( ph -> ( ExtStrCat ` U ) = { <. ( Base ` ndx ) , U >. , <. ( Hom ` ndx ) , H >. , <. ( comp ` ndx ) , .x. >. } ) | 
						
							| 24 | 1 23 | eqtrid |  |-  ( ph -> C = { <. ( Base ` ndx ) , U >. , <. ( Hom ` ndx ) , H >. , <. ( comp ` ndx ) , .x. >. } ) |