| Step | Hyp | Ref | Expression | 
						
							| 1 |  | mamufval.f |  |-  F = ( R maMul <. M , N , P >. ) | 
						
							| 2 |  | mamufval.b |  |-  B = ( Base ` R ) | 
						
							| 3 |  | mamufval.t |  |-  .x. = ( .r ` R ) | 
						
							| 4 |  | mamufval.r |  |-  ( ph -> R e. V ) | 
						
							| 5 |  | mamufval.m |  |-  ( ph -> M e. Fin ) | 
						
							| 6 |  | mamufval.n |  |-  ( ph -> N e. Fin ) | 
						
							| 7 |  | mamufval.p |  |-  ( ph -> P e. Fin ) | 
						
							| 8 |  | df-mamu |  |-  maMul = ( r e. _V , o e. _V |-> [_ ( 1st ` ( 1st ` o ) ) / m ]_ [_ ( 2nd ` ( 1st ` o ) ) / n ]_ [_ ( 2nd ` o ) / p ]_ ( x e. ( ( Base ` r ) ^m ( m X. n ) ) , y e. ( ( Base ` r ) ^m ( n X. p ) ) |-> ( i e. m , k e. p |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) ) | 
						
							| 9 | 8 | a1i |  |-  ( ph -> maMul = ( r e. _V , o e. _V |-> [_ ( 1st ` ( 1st ` o ) ) / m ]_ [_ ( 2nd ` ( 1st ` o ) ) / n ]_ [_ ( 2nd ` o ) / p ]_ ( x e. ( ( Base ` r ) ^m ( m X. n ) ) , y e. ( ( Base ` r ) ^m ( n X. p ) ) |-> ( i e. m , k e. p |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) ) ) | 
						
							| 10 |  | fvex |  |-  ( 1st ` ( 1st ` o ) ) e. _V | 
						
							| 11 |  | fvex |  |-  ( 2nd ` ( 1st ` o ) ) e. _V | 
						
							| 12 |  | fvex |  |-  ( 2nd ` o ) e. _V | 
						
							| 13 |  | eqidd |  |-  ( p = ( 2nd ` o ) -> ( ( Base ` r ) ^m ( m X. n ) ) = ( ( Base ` r ) ^m ( m X. n ) ) ) | 
						
							| 14 |  | xpeq2 |  |-  ( p = ( 2nd ` o ) -> ( n X. p ) = ( n X. ( 2nd ` o ) ) ) | 
						
							| 15 | 14 | oveq2d |  |-  ( p = ( 2nd ` o ) -> ( ( Base ` r ) ^m ( n X. p ) ) = ( ( Base ` r ) ^m ( n X. ( 2nd ` o ) ) ) ) | 
						
							| 16 |  | eqidd |  |-  ( p = ( 2nd ` o ) -> m = m ) | 
						
							| 17 |  | id |  |-  ( p = ( 2nd ` o ) -> p = ( 2nd ` o ) ) | 
						
							| 18 |  | eqidd |  |-  ( p = ( 2nd ` o ) -> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) = ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) | 
						
							| 19 | 16 17 18 | mpoeq123dv |  |-  ( p = ( 2nd ` o ) -> ( i e. m , k e. p |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) = ( i e. m , k e. ( 2nd ` o ) |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) | 
						
							| 20 | 13 15 19 | mpoeq123dv |  |-  ( p = ( 2nd ` o ) -> ( x e. ( ( Base ` r ) ^m ( m X. n ) ) , y e. ( ( Base ` r ) ^m ( n X. p ) ) |-> ( i e. m , k e. p |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) = ( x e. ( ( Base ` r ) ^m ( m X. n ) ) , y e. ( ( Base ` r ) ^m ( n X. ( 2nd ` o ) ) ) |-> ( i e. m , k e. ( 2nd ` o ) |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) ) | 
						
							| 21 | 12 20 | csbie |  |-  [_ ( 2nd ` o ) / p ]_ ( x e. ( ( Base ` r ) ^m ( m X. n ) ) , y e. ( ( Base ` r ) ^m ( n X. p ) ) |-> ( i e. m , k e. p |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) = ( x e. ( ( Base ` r ) ^m ( m X. n ) ) , y e. ( ( Base ` r ) ^m ( n X. ( 2nd ` o ) ) ) |-> ( i e. m , k e. ( 2nd ` o ) |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) | 
						
							| 22 |  | xpeq12 |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> ( m X. n ) = ( ( 1st ` ( 1st ` o ) ) X. ( 2nd ` ( 1st ` o ) ) ) ) | 
						
							| 23 | 22 | oveq2d |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> ( ( Base ` r ) ^m ( m X. n ) ) = ( ( Base ` r ) ^m ( ( 1st ` ( 1st ` o ) ) X. ( 2nd ` ( 1st ` o ) ) ) ) ) | 
						
							| 24 |  | simpr |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> n = ( 2nd ` ( 1st ` o ) ) ) | 
						
							| 25 | 24 | xpeq1d |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> ( n X. ( 2nd ` o ) ) = ( ( 2nd ` ( 1st ` o ) ) X. ( 2nd ` o ) ) ) | 
						
							| 26 | 25 | oveq2d |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> ( ( Base ` r ) ^m ( n X. ( 2nd ` o ) ) ) = ( ( Base ` r ) ^m ( ( 2nd ` ( 1st ` o ) ) X. ( 2nd ` o ) ) ) ) | 
						
							| 27 |  | id |  |-  ( m = ( 1st ` ( 1st ` o ) ) -> m = ( 1st ` ( 1st ` o ) ) ) | 
						
							| 28 | 27 | adantr |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> m = ( 1st ` ( 1st ` o ) ) ) | 
						
							| 29 |  | eqidd |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> ( 2nd ` o ) = ( 2nd ` o ) ) | 
						
							| 30 |  | eqidd |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> ( ( i x j ) ( .r ` r ) ( j y k ) ) = ( ( i x j ) ( .r ` r ) ( j y k ) ) ) | 
						
							| 31 | 24 30 | mpteq12dv |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) = ( j e. ( 2nd ` ( 1st ` o ) ) |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) | 
						
							| 32 | 31 | oveq2d |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) = ( r gsum ( j e. ( 2nd ` ( 1st ` o ) ) |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) | 
						
							| 33 | 28 29 32 | mpoeq123dv |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> ( i e. m , k e. ( 2nd ` o ) |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) = ( i e. ( 1st ` ( 1st ` o ) ) , k e. ( 2nd ` o ) |-> ( r gsum ( j e. ( 2nd ` ( 1st ` o ) ) |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) | 
						
							| 34 | 23 26 33 | mpoeq123dv |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> ( x e. ( ( Base ` r ) ^m ( m X. n ) ) , y e. ( ( Base ` r ) ^m ( n X. ( 2nd ` o ) ) ) |-> ( i e. m , k e. ( 2nd ` o ) |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) = ( x e. ( ( Base ` r ) ^m ( ( 1st ` ( 1st ` o ) ) X. ( 2nd ` ( 1st ` o ) ) ) ) , y e. ( ( Base ` r ) ^m ( ( 2nd ` ( 1st ` o ) ) X. ( 2nd ` o ) ) ) |-> ( i e. ( 1st ` ( 1st ` o ) ) , k e. ( 2nd ` o ) |-> ( r gsum ( j e. ( 2nd ` ( 1st ` o ) ) |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) ) | 
						
							| 35 | 21 34 | eqtrid |  |-  ( ( m = ( 1st ` ( 1st ` o ) ) /\ n = ( 2nd ` ( 1st ` o ) ) ) -> [_ ( 2nd ` o ) / p ]_ ( x e. ( ( Base ` r ) ^m ( m X. n ) ) , y e. ( ( Base ` r ) ^m ( n X. p ) ) |-> ( i e. m , k e. p |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) = ( x e. ( ( Base ` r ) ^m ( ( 1st ` ( 1st ` o ) ) X. ( 2nd ` ( 1st ` o ) ) ) ) , y e. ( ( Base ` r ) ^m ( ( 2nd ` ( 1st ` o ) ) X. ( 2nd ` o ) ) ) |-> ( i e. ( 1st ` ( 1st ` o ) ) , k e. ( 2nd ` o ) |-> ( r gsum ( j e. ( 2nd ` ( 1st ` o ) ) |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) ) | 
						
							| 36 | 10 11 35 | csbie2 |  |-  [_ ( 1st ` ( 1st ` o ) ) / m ]_ [_ ( 2nd ` ( 1st ` o ) ) / n ]_ [_ ( 2nd ` o ) / p ]_ ( x e. ( ( Base ` r ) ^m ( m X. n ) ) , y e. ( ( Base ` r ) ^m ( n X. p ) ) |-> ( i e. m , k e. p |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) = ( x e. ( ( Base ` r ) ^m ( ( 1st ` ( 1st ` o ) ) X. ( 2nd ` ( 1st ` o ) ) ) ) , y e. ( ( Base ` r ) ^m ( ( 2nd ` ( 1st ` o ) ) X. ( 2nd ` o ) ) ) |-> ( i e. ( 1st ` ( 1st ` o ) ) , k e. ( 2nd ` o ) |-> ( r gsum ( j e. ( 2nd ` ( 1st ` o ) ) |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) | 
						
							| 37 |  | simprl |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> r = R ) | 
						
							| 38 | 37 | fveq2d |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( Base ` r ) = ( Base ` R ) ) | 
						
							| 39 | 38 2 | eqtr4di |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( Base ` r ) = B ) | 
						
							| 40 |  | fveq2 |  |-  ( o = <. M , N , P >. -> ( 1st ` o ) = ( 1st ` <. M , N , P >. ) ) | 
						
							| 41 | 40 | fveq2d |  |-  ( o = <. M , N , P >. -> ( 1st ` ( 1st ` o ) ) = ( 1st ` ( 1st ` <. M , N , P >. ) ) ) | 
						
							| 42 | 41 | ad2antll |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( 1st ` ( 1st ` o ) ) = ( 1st ` ( 1st ` <. M , N , P >. ) ) ) | 
						
							| 43 |  | ot1stg |  |-  ( ( M e. Fin /\ N e. Fin /\ P e. Fin ) -> ( 1st ` ( 1st ` <. M , N , P >. ) ) = M ) | 
						
							| 44 | 5 6 7 43 | syl3anc |  |-  ( ph -> ( 1st ` ( 1st ` <. M , N , P >. ) ) = M ) | 
						
							| 45 | 44 | adantr |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( 1st ` ( 1st ` <. M , N , P >. ) ) = M ) | 
						
							| 46 | 42 45 | eqtrd |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( 1st ` ( 1st ` o ) ) = M ) | 
						
							| 47 | 40 | fveq2d |  |-  ( o = <. M , N , P >. -> ( 2nd ` ( 1st ` o ) ) = ( 2nd ` ( 1st ` <. M , N , P >. ) ) ) | 
						
							| 48 | 47 | ad2antll |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( 2nd ` ( 1st ` o ) ) = ( 2nd ` ( 1st ` <. M , N , P >. ) ) ) | 
						
							| 49 |  | ot2ndg |  |-  ( ( M e. Fin /\ N e. Fin /\ P e. Fin ) -> ( 2nd ` ( 1st ` <. M , N , P >. ) ) = N ) | 
						
							| 50 | 5 6 7 49 | syl3anc |  |-  ( ph -> ( 2nd ` ( 1st ` <. M , N , P >. ) ) = N ) | 
						
							| 51 | 50 | adantr |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( 2nd ` ( 1st ` <. M , N , P >. ) ) = N ) | 
						
							| 52 | 48 51 | eqtrd |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( 2nd ` ( 1st ` o ) ) = N ) | 
						
							| 53 | 46 52 | xpeq12d |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( ( 1st ` ( 1st ` o ) ) X. ( 2nd ` ( 1st ` o ) ) ) = ( M X. N ) ) | 
						
							| 54 | 39 53 | oveq12d |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( ( Base ` r ) ^m ( ( 1st ` ( 1st ` o ) ) X. ( 2nd ` ( 1st ` o ) ) ) ) = ( B ^m ( M X. N ) ) ) | 
						
							| 55 |  | fveq2 |  |-  ( o = <. M , N , P >. -> ( 2nd ` o ) = ( 2nd ` <. M , N , P >. ) ) | 
						
							| 56 | 55 | ad2antll |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( 2nd ` o ) = ( 2nd ` <. M , N , P >. ) ) | 
						
							| 57 |  | ot3rdg |  |-  ( P e. Fin -> ( 2nd ` <. M , N , P >. ) = P ) | 
						
							| 58 | 7 57 | syl |  |-  ( ph -> ( 2nd ` <. M , N , P >. ) = P ) | 
						
							| 59 | 58 | adantr |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( 2nd ` <. M , N , P >. ) = P ) | 
						
							| 60 | 56 59 | eqtrd |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( 2nd ` o ) = P ) | 
						
							| 61 | 52 60 | xpeq12d |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( ( 2nd ` ( 1st ` o ) ) X. ( 2nd ` o ) ) = ( N X. P ) ) | 
						
							| 62 | 39 61 | oveq12d |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( ( Base ` r ) ^m ( ( 2nd ` ( 1st ` o ) ) X. ( 2nd ` o ) ) ) = ( B ^m ( N X. P ) ) ) | 
						
							| 63 | 37 | fveq2d |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( .r ` r ) = ( .r ` R ) ) | 
						
							| 64 | 63 3 | eqtr4di |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( .r ` r ) = .x. ) | 
						
							| 65 | 64 | oveqd |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( ( i x j ) ( .r ` r ) ( j y k ) ) = ( ( i x j ) .x. ( j y k ) ) ) | 
						
							| 66 | 52 65 | mpteq12dv |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( j e. ( 2nd ` ( 1st ` o ) ) |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) = ( j e. N |-> ( ( i x j ) .x. ( j y k ) ) ) ) | 
						
							| 67 | 37 66 | oveq12d |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( r gsum ( j e. ( 2nd ` ( 1st ` o ) ) |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) = ( R gsum ( j e. N |-> ( ( i x j ) .x. ( j y k ) ) ) ) ) | 
						
							| 68 | 46 60 67 | mpoeq123dv |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( i e. ( 1st ` ( 1st ` o ) ) , k e. ( 2nd ` o ) |-> ( r gsum ( j e. ( 2nd ` ( 1st ` o ) ) |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) = ( i e. M , k e. P |-> ( R gsum ( j e. N |-> ( ( i x j ) .x. ( j y k ) ) ) ) ) ) | 
						
							| 69 | 54 62 68 | mpoeq123dv |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> ( x e. ( ( Base ` r ) ^m ( ( 1st ` ( 1st ` o ) ) X. ( 2nd ` ( 1st ` o ) ) ) ) , y e. ( ( Base ` r ) ^m ( ( 2nd ` ( 1st ` o ) ) X. ( 2nd ` o ) ) ) |-> ( i e. ( 1st ` ( 1st ` o ) ) , k e. ( 2nd ` o ) |-> ( r gsum ( j e. ( 2nd ` ( 1st ` o ) ) |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) = ( x e. ( B ^m ( M X. N ) ) , y e. ( B ^m ( N X. P ) ) |-> ( i e. M , k e. P |-> ( R gsum ( j e. N |-> ( ( i x j ) .x. ( j y k ) ) ) ) ) ) ) | 
						
							| 70 | 36 69 | eqtrid |  |-  ( ( ph /\ ( r = R /\ o = <. M , N , P >. ) ) -> [_ ( 1st ` ( 1st ` o ) ) / m ]_ [_ ( 2nd ` ( 1st ` o ) ) / n ]_ [_ ( 2nd ` o ) / p ]_ ( x e. ( ( Base ` r ) ^m ( m X. n ) ) , y e. ( ( Base ` r ) ^m ( n X. p ) ) |-> ( i e. m , k e. p |-> ( r gsum ( j e. n |-> ( ( i x j ) ( .r ` r ) ( j y k ) ) ) ) ) ) = ( x e. ( B ^m ( M X. N ) ) , y e. ( B ^m ( N X. P ) ) |-> ( i e. M , k e. P |-> ( R gsum ( j e. N |-> ( ( i x j ) .x. ( j y k ) ) ) ) ) ) ) | 
						
							| 71 | 4 | elexd |  |-  ( ph -> R e. _V ) | 
						
							| 72 |  | otex |  |-  <. M , N , P >. e. _V | 
						
							| 73 | 72 | a1i |  |-  ( ph -> <. M , N , P >. e. _V ) | 
						
							| 74 |  | ovex |  |-  ( B ^m ( M X. N ) ) e. _V | 
						
							| 75 |  | ovex |  |-  ( B ^m ( N X. P ) ) e. _V | 
						
							| 76 | 74 75 | mpoex |  |-  ( x e. ( B ^m ( M X. N ) ) , y e. ( B ^m ( N X. P ) ) |-> ( i e. M , k e. P |-> ( R gsum ( j e. N |-> ( ( i x j ) .x. ( j y k ) ) ) ) ) ) e. _V | 
						
							| 77 | 76 | a1i |  |-  ( ph -> ( x e. ( B ^m ( M X. N ) ) , y e. ( B ^m ( N X. P ) ) |-> ( i e. M , k e. P |-> ( R gsum ( j e. N |-> ( ( i x j ) .x. ( j y k ) ) ) ) ) ) e. _V ) | 
						
							| 78 | 9 70 71 73 77 | ovmpod |  |-  ( ph -> ( R maMul <. M , N , P >. ) = ( x e. ( B ^m ( M X. N ) ) , y e. ( B ^m ( N X. P ) ) |-> ( i e. M , k e. P |-> ( R gsum ( j e. N |-> ( ( i x j ) .x. ( j y k ) ) ) ) ) ) ) | 
						
							| 79 | 1 78 | eqtrid |  |-  ( ph -> F = ( x e. ( B ^m ( M X. N ) ) , y e. ( B ^m ( N X. P ) ) |-> ( i e. M , k e. P |-> ( R gsum ( j e. N |-> ( ( i x j ) .x. ( j y k ) ) ) ) ) ) ) |