| Step | Hyp | Ref | Expression | 
						
							| 1 |  | caonncan.i |  |-  ( ph -> I e. V ) | 
						
							| 2 |  | caonncan.a |  |-  ( ph -> A : I --> S ) | 
						
							| 3 |  | caonncan.b |  |-  ( ph -> B : I --> S ) | 
						
							| 4 |  | caonncan.z |  |-  ( ( ph /\ ( x e. S /\ y e. S ) ) -> ( x M ( x M y ) ) = y ) | 
						
							| 5 | 2 | ffvelcdmda |  |-  ( ( ph /\ z e. I ) -> ( A ` z ) e. S ) | 
						
							| 6 | 3 | ffvelcdmda |  |-  ( ( ph /\ z e. I ) -> ( B ` z ) e. S ) | 
						
							| 7 | 4 | ralrimivva |  |-  ( ph -> A. x e. S A. y e. S ( x M ( x M y ) ) = y ) | 
						
							| 8 | 7 | adantr |  |-  ( ( ph /\ z e. I ) -> A. x e. S A. y e. S ( x M ( x M y ) ) = y ) | 
						
							| 9 |  | id |  |-  ( x = ( A ` z ) -> x = ( A ` z ) ) | 
						
							| 10 |  | oveq1 |  |-  ( x = ( A ` z ) -> ( x M y ) = ( ( A ` z ) M y ) ) | 
						
							| 11 | 9 10 | oveq12d |  |-  ( x = ( A ` z ) -> ( x M ( x M y ) ) = ( ( A ` z ) M ( ( A ` z ) M y ) ) ) | 
						
							| 12 | 11 | eqeq1d |  |-  ( x = ( A ` z ) -> ( ( x M ( x M y ) ) = y <-> ( ( A ` z ) M ( ( A ` z ) M y ) ) = y ) ) | 
						
							| 13 |  | oveq2 |  |-  ( y = ( B ` z ) -> ( ( A ` z ) M y ) = ( ( A ` z ) M ( B ` z ) ) ) | 
						
							| 14 | 13 | oveq2d |  |-  ( y = ( B ` z ) -> ( ( A ` z ) M ( ( A ` z ) M y ) ) = ( ( A ` z ) M ( ( A ` z ) M ( B ` z ) ) ) ) | 
						
							| 15 |  | id |  |-  ( y = ( B ` z ) -> y = ( B ` z ) ) | 
						
							| 16 | 14 15 | eqeq12d |  |-  ( y = ( B ` z ) -> ( ( ( A ` z ) M ( ( A ` z ) M y ) ) = y <-> ( ( A ` z ) M ( ( A ` z ) M ( B ` z ) ) ) = ( B ` z ) ) ) | 
						
							| 17 | 12 16 | rspc2va |  |-  ( ( ( ( A ` z ) e. S /\ ( B ` z ) e. S ) /\ A. x e. S A. y e. S ( x M ( x M y ) ) = y ) -> ( ( A ` z ) M ( ( A ` z ) M ( B ` z ) ) ) = ( B ` z ) ) | 
						
							| 18 | 5 6 8 17 | syl21anc |  |-  ( ( ph /\ z e. I ) -> ( ( A ` z ) M ( ( A ` z ) M ( B ` z ) ) ) = ( B ` z ) ) | 
						
							| 19 | 18 | mpteq2dva |  |-  ( ph -> ( z e. I |-> ( ( A ` z ) M ( ( A ` z ) M ( B ` z ) ) ) ) = ( z e. I |-> ( B ` z ) ) ) | 
						
							| 20 |  | fvexd |  |-  ( ( ph /\ z e. I ) -> ( A ` z ) e. _V ) | 
						
							| 21 |  | ovexd |  |-  ( ( ph /\ z e. I ) -> ( ( A ` z ) M ( B ` z ) ) e. _V ) | 
						
							| 22 | 2 | feqmptd |  |-  ( ph -> A = ( z e. I |-> ( A ` z ) ) ) | 
						
							| 23 |  | fvexd |  |-  ( ( ph /\ z e. I ) -> ( B ` z ) e. _V ) | 
						
							| 24 | 3 | feqmptd |  |-  ( ph -> B = ( z e. I |-> ( B ` z ) ) ) | 
						
							| 25 | 1 20 23 22 24 | offval2 |  |-  ( ph -> ( A oF M B ) = ( z e. I |-> ( ( A ` z ) M ( B ` z ) ) ) ) | 
						
							| 26 | 1 20 21 22 25 | offval2 |  |-  ( ph -> ( A oF M ( A oF M B ) ) = ( z e. I |-> ( ( A ` z ) M ( ( A ` z ) M ( B ` z ) ) ) ) ) | 
						
							| 27 | 19 26 24 | 3eqtr4d |  |-  ( ph -> ( A oF M ( A oF M B ) ) = B ) |