| Step | Hyp | Ref | Expression | 
						
							| 1 |  | rngcbasALTV.c |  |-  C = ( RngCatALTV ` U ) | 
						
							| 2 |  | rngcbasALTV.b |  |-  B = ( Base ` C ) | 
						
							| 3 |  | rngcbasALTV.u |  |-  ( ph -> U e. V ) | 
						
							| 4 |  | rngccofvalALTV.o |  |-  .x. = ( comp ` C ) | 
						
							| 5 | 1 2 3 | rngcbasALTV |  |-  ( ph -> B = ( U i^i Rng ) ) | 
						
							| 6 |  | eqid |  |-  ( Hom ` C ) = ( Hom ` C ) | 
						
							| 7 | 1 2 3 6 | rngchomfvalALTV |  |-  ( ph -> ( Hom ` C ) = ( x e. B , y e. B |-> ( x RngHom y ) ) ) | 
						
							| 8 |  | eqidd |  |-  ( ph -> ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) = ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) ) | 
						
							| 9 | 1 3 5 7 8 | rngcvalALTV |  |-  ( ph -> C = { <. ( Base ` ndx ) , B >. , <. ( Hom ` ndx ) , ( Hom ` C ) >. , <. ( comp ` ndx ) , ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) >. } ) | 
						
							| 10 | 9 | fveq2d |  |-  ( ph -> ( comp ` C ) = ( comp ` { <. ( Base ` ndx ) , B >. , <. ( Hom ` ndx ) , ( Hom ` C ) >. , <. ( comp ` ndx ) , ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) >. } ) ) | 
						
							| 11 | 2 | fvexi |  |-  B e. _V | 
						
							| 12 |  | sqxpexg |  |-  ( B e. _V -> ( B X. B ) e. _V ) | 
						
							| 13 | 11 12 | ax-mp |  |-  ( B X. B ) e. _V | 
						
							| 14 | 13 11 | mpoex |  |-  ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) e. _V | 
						
							| 15 |  | catstr |  |-  { <. ( Base ` ndx ) , B >. , <. ( Hom ` ndx ) , ( Hom ` C ) >. , <. ( comp ` ndx ) , ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) >. } Struct <. 1 , ; 1 5 >. | 
						
							| 16 |  | ccoid |  |-  comp = Slot ( comp ` ndx ) | 
						
							| 17 |  | snsstp3 |  |-  { <. ( comp ` ndx ) , ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) >. } C_ { <. ( Base ` ndx ) , B >. , <. ( Hom ` ndx ) , ( Hom ` C ) >. , <. ( comp ` ndx ) , ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) >. } | 
						
							| 18 | 15 16 17 | strfv |  |-  ( ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) e. _V -> ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) = ( comp ` { <. ( Base ` ndx ) , B >. , <. ( Hom ` ndx ) , ( Hom ` C ) >. , <. ( comp ` ndx ) , ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) >. } ) ) | 
						
							| 19 | 14 18 | ax-mp |  |-  ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) = ( comp ` { <. ( Base ` ndx ) , B >. , <. ( Hom ` ndx ) , ( Hom ` C ) >. , <. ( comp ` ndx ) , ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) >. } ) | 
						
							| 20 | 10 4 19 | 3eqtr4g |  |-  ( ph -> .x. = ( v e. ( B X. B ) , z e. B |-> ( g e. ( ( 2nd ` v ) RngHom z ) , f e. ( ( 1st ` v ) RngHom ( 2nd ` v ) ) |-> ( g o. f ) ) ) ) |