| Step | Hyp | Ref | Expression | 
						
							| 1 |  | dsmmval.b |  |-  B = { f e. ( Base ` ( S Xs_ R ) ) | { x e. dom R | ( f ` x ) =/= ( 0g ` ( R ` x ) ) } e. Fin } | 
						
							| 2 |  | elex |  |-  ( R e. V -> R e. _V ) | 
						
							| 3 |  | oveq12 |  |-  ( ( s = S /\ r = R ) -> ( s Xs_ r ) = ( S Xs_ R ) ) | 
						
							| 4 |  | eqid |  |-  ( s Xs_ r ) = ( s Xs_ r ) | 
						
							| 5 |  | vex |  |-  s e. _V | 
						
							| 6 | 5 | a1i |  |-  ( ( s = S /\ r = R ) -> s e. _V ) | 
						
							| 7 |  | vex |  |-  r e. _V | 
						
							| 8 | 7 | a1i |  |-  ( ( s = S /\ r = R ) -> r e. _V ) | 
						
							| 9 |  | eqid |  |-  ( Base ` ( s Xs_ r ) ) = ( Base ` ( s Xs_ r ) ) | 
						
							| 10 |  | eqidd |  |-  ( ( s = S /\ r = R ) -> dom r = dom r ) | 
						
							| 11 | 4 6 8 9 10 | prdsbas |  |-  ( ( s = S /\ r = R ) -> ( Base ` ( s Xs_ r ) ) = X_ x e. dom r ( Base ` ( r ` x ) ) ) | 
						
							| 12 | 3 | fveq2d |  |-  ( ( s = S /\ r = R ) -> ( Base ` ( s Xs_ r ) ) = ( Base ` ( S Xs_ R ) ) ) | 
						
							| 13 | 11 12 | eqtr3d |  |-  ( ( s = S /\ r = R ) -> X_ x e. dom r ( Base ` ( r ` x ) ) = ( Base ` ( S Xs_ R ) ) ) | 
						
							| 14 |  | simpr |  |-  ( ( s = S /\ r = R ) -> r = R ) | 
						
							| 15 | 14 | dmeqd |  |-  ( ( s = S /\ r = R ) -> dom r = dom R ) | 
						
							| 16 | 14 | fveq1d |  |-  ( ( s = S /\ r = R ) -> ( r ` x ) = ( R ` x ) ) | 
						
							| 17 | 16 | fveq2d |  |-  ( ( s = S /\ r = R ) -> ( 0g ` ( r ` x ) ) = ( 0g ` ( R ` x ) ) ) | 
						
							| 18 | 17 | neeq2d |  |-  ( ( s = S /\ r = R ) -> ( ( f ` x ) =/= ( 0g ` ( r ` x ) ) <-> ( f ` x ) =/= ( 0g ` ( R ` x ) ) ) ) | 
						
							| 19 | 15 18 | rabeqbidv |  |-  ( ( s = S /\ r = R ) -> { x e. dom r | ( f ` x ) =/= ( 0g ` ( r ` x ) ) } = { x e. dom R | ( f ` x ) =/= ( 0g ` ( R ` x ) ) } ) | 
						
							| 20 | 19 | eleq1d |  |-  ( ( s = S /\ r = R ) -> ( { x e. dom r | ( f ` x ) =/= ( 0g ` ( r ` x ) ) } e. Fin <-> { x e. dom R | ( f ` x ) =/= ( 0g ` ( R ` x ) ) } e. Fin ) ) | 
						
							| 21 | 13 20 | rabeqbidv |  |-  ( ( s = S /\ r = R ) -> { f e. X_ x e. dom r ( Base ` ( r ` x ) ) | { x e. dom r | ( f ` x ) =/= ( 0g ` ( r ` x ) ) } e. Fin } = { f e. ( Base ` ( S Xs_ R ) ) | { x e. dom R | ( f ` x ) =/= ( 0g ` ( R ` x ) ) } e. Fin } ) | 
						
							| 22 | 21 1 | eqtr4di |  |-  ( ( s = S /\ r = R ) -> { f e. X_ x e. dom r ( Base ` ( r ` x ) ) | { x e. dom r | ( f ` x ) =/= ( 0g ` ( r ` x ) ) } e. Fin } = B ) | 
						
							| 23 | 3 22 | oveq12d |  |-  ( ( s = S /\ r = R ) -> ( ( s Xs_ r ) |`s { f e. X_ x e. dom r ( Base ` ( r ` x ) ) | { x e. dom r | ( f ` x ) =/= ( 0g ` ( r ` x ) ) } e. Fin } ) = ( ( S Xs_ R ) |`s B ) ) | 
						
							| 24 |  | df-dsmm |  |-  (+)m = ( s e. _V , r e. _V |-> ( ( s Xs_ r ) |`s { f e. X_ x e. dom r ( Base ` ( r ` x ) ) | { x e. dom r | ( f ` x ) =/= ( 0g ` ( r ` x ) ) } e. Fin } ) ) | 
						
							| 25 |  | ovex |  |-  ( ( S Xs_ R ) |`s B ) e. _V | 
						
							| 26 | 23 24 25 | ovmpoa |  |-  ( ( S e. _V /\ R e. _V ) -> ( S (+)m R ) = ( ( S Xs_ R ) |`s B ) ) | 
						
							| 27 |  | reldmdsmm |  |-  Rel dom (+)m | 
						
							| 28 | 27 | ovprc1 |  |-  ( -. S e. _V -> ( S (+)m R ) = (/) ) | 
						
							| 29 |  | ress0 |  |-  ( (/) |`s B ) = (/) | 
						
							| 30 | 28 29 | eqtr4di |  |-  ( -. S e. _V -> ( S (+)m R ) = ( (/) |`s B ) ) | 
						
							| 31 |  | reldmprds |  |-  Rel dom Xs_ | 
						
							| 32 | 31 | ovprc1 |  |-  ( -. S e. _V -> ( S Xs_ R ) = (/) ) | 
						
							| 33 | 32 | oveq1d |  |-  ( -. S e. _V -> ( ( S Xs_ R ) |`s B ) = ( (/) |`s B ) ) | 
						
							| 34 | 30 33 | eqtr4d |  |-  ( -. S e. _V -> ( S (+)m R ) = ( ( S Xs_ R ) |`s B ) ) | 
						
							| 35 | 34 | adantr |  |-  ( ( -. S e. _V /\ R e. _V ) -> ( S (+)m R ) = ( ( S Xs_ R ) |`s B ) ) | 
						
							| 36 | 26 35 | pm2.61ian |  |-  ( R e. _V -> ( S (+)m R ) = ( ( S Xs_ R ) |`s B ) ) | 
						
							| 37 | 2 36 | syl |  |-  ( R e. V -> ( S (+)m R ) = ( ( S Xs_ R ) |`s B ) ) |