| Step | Hyp | Ref | Expression | 
						
							| 1 |  | ovex |  |-  ( ( ( bra ` A ) ` B ) x. ( ( bra ` C ) ` x ) ) e. _V | 
						
							| 2 |  | eqid |  |-  ( x e. ~H |-> ( ( ( bra ` A ) ` B ) x. ( ( bra ` C ) ` x ) ) ) = ( x e. ~H |-> ( ( ( bra ` A ) ` B ) x. ( ( bra ` C ) ` x ) ) ) | 
						
							| 3 | 1 2 | fnmpti |  |-  ( x e. ~H |-> ( ( ( bra ` A ) ` B ) x. ( ( bra ` C ) ` x ) ) ) Fn ~H | 
						
							| 4 |  | bracl |  |-  ( ( A e. ~H /\ B e. ~H ) -> ( ( bra ` A ) ` B ) e. CC ) | 
						
							| 5 |  | brafn |  |-  ( C e. ~H -> ( bra ` C ) : ~H --> CC ) | 
						
							| 6 |  | hfmmval |  |-  ( ( ( ( bra ` A ) ` B ) e. CC /\ ( bra ` C ) : ~H --> CC ) -> ( ( ( bra ` A ) ` B ) .fn ( bra ` C ) ) = ( x e. ~H |-> ( ( ( bra ` A ) ` B ) x. ( ( bra ` C ) ` x ) ) ) ) | 
						
							| 7 | 4 5 6 | syl2an |  |-  ( ( ( A e. ~H /\ B e. ~H ) /\ C e. ~H ) -> ( ( ( bra ` A ) ` B ) .fn ( bra ` C ) ) = ( x e. ~H |-> ( ( ( bra ` A ) ` B ) x. ( ( bra ` C ) ` x ) ) ) ) | 
						
							| 8 | 7 | 3impa |  |-  ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) -> ( ( ( bra ` A ) ` B ) .fn ( bra ` C ) ) = ( x e. ~H |-> ( ( ( bra ` A ) ` B ) x. ( ( bra ` C ) ` x ) ) ) ) | 
						
							| 9 | 8 | fneq1d |  |-  ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) -> ( ( ( ( bra ` A ) ` B ) .fn ( bra ` C ) ) Fn ~H <-> ( x e. ~H |-> ( ( ( bra ` A ) ` B ) x. ( ( bra ` C ) ` x ) ) ) Fn ~H ) ) | 
						
							| 10 | 3 9 | mpbiri |  |-  ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) -> ( ( ( bra ` A ) ` B ) .fn ( bra ` C ) ) Fn ~H ) | 
						
							| 11 |  | brafn |  |-  ( A e. ~H -> ( bra ` A ) : ~H --> CC ) | 
						
							| 12 |  | kbop |  |-  ( ( B e. ~H /\ C e. ~H ) -> ( B ketbra C ) : ~H --> ~H ) | 
						
							| 13 |  | fco |  |-  ( ( ( bra ` A ) : ~H --> CC /\ ( B ketbra C ) : ~H --> ~H ) -> ( ( bra ` A ) o. ( B ketbra C ) ) : ~H --> CC ) | 
						
							| 14 | 11 12 13 | syl2an |  |-  ( ( A e. ~H /\ ( B e. ~H /\ C e. ~H ) ) -> ( ( bra ` A ) o. ( B ketbra C ) ) : ~H --> CC ) | 
						
							| 15 | 14 | 3impb |  |-  ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) -> ( ( bra ` A ) o. ( B ketbra C ) ) : ~H --> CC ) | 
						
							| 16 | 15 | ffnd |  |-  ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) -> ( ( bra ` A ) o. ( B ketbra C ) ) Fn ~H ) | 
						
							| 17 |  | simpl1 |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> A e. ~H ) | 
						
							| 18 |  | simpl2 |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> B e. ~H ) | 
						
							| 19 |  | braval |  |-  ( ( A e. ~H /\ B e. ~H ) -> ( ( bra ` A ) ` B ) = ( B .ih A ) ) | 
						
							| 20 | 17 18 19 | syl2anc |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( bra ` A ) ` B ) = ( B .ih A ) ) | 
						
							| 21 |  | simpl3 |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> C e. ~H ) | 
						
							| 22 |  | simpr |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> x e. ~H ) | 
						
							| 23 |  | braval |  |-  ( ( C e. ~H /\ x e. ~H ) -> ( ( bra ` C ) ` x ) = ( x .ih C ) ) | 
						
							| 24 | 21 22 23 | syl2anc |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( bra ` C ) ` x ) = ( x .ih C ) ) | 
						
							| 25 | 20 24 | oveq12d |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( ( bra ` A ) ` B ) x. ( ( bra ` C ) ` x ) ) = ( ( B .ih A ) x. ( x .ih C ) ) ) | 
						
							| 26 |  | hicl |  |-  ( ( B e. ~H /\ A e. ~H ) -> ( B .ih A ) e. CC ) | 
						
							| 27 | 18 17 26 | syl2anc |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( B .ih A ) e. CC ) | 
						
							| 28 | 20 27 | eqeltrd |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( bra ` A ) ` B ) e. CC ) | 
						
							| 29 | 21 5 | syl |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( bra ` C ) : ~H --> CC ) | 
						
							| 30 |  | hfmval |  |-  ( ( ( ( bra ` A ) ` B ) e. CC /\ ( bra ` C ) : ~H --> CC /\ x e. ~H ) -> ( ( ( ( bra ` A ) ` B ) .fn ( bra ` C ) ) ` x ) = ( ( ( bra ` A ) ` B ) x. ( ( bra ` C ) ` x ) ) ) | 
						
							| 31 | 28 29 22 30 | syl3anc |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( ( ( bra ` A ) ` B ) .fn ( bra ` C ) ) ` x ) = ( ( ( bra ` A ) ` B ) x. ( ( bra ` C ) ` x ) ) ) | 
						
							| 32 |  | hicl |  |-  ( ( x e. ~H /\ C e. ~H ) -> ( x .ih C ) e. CC ) | 
						
							| 33 | 22 21 32 | syl2anc |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( x .ih C ) e. CC ) | 
						
							| 34 |  | ax-his3 |  |-  ( ( ( x .ih C ) e. CC /\ B e. ~H /\ A e. ~H ) -> ( ( ( x .ih C ) .h B ) .ih A ) = ( ( x .ih C ) x. ( B .ih A ) ) ) | 
						
							| 35 | 33 18 17 34 | syl3anc |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( ( x .ih C ) .h B ) .ih A ) = ( ( x .ih C ) x. ( B .ih A ) ) ) | 
						
							| 36 | 12 | 3adant1 |  |-  ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) -> ( B ketbra C ) : ~H --> ~H ) | 
						
							| 37 |  | fvco3 |  |-  ( ( ( B ketbra C ) : ~H --> ~H /\ x e. ~H ) -> ( ( ( bra ` A ) o. ( B ketbra C ) ) ` x ) = ( ( bra ` A ) ` ( ( B ketbra C ) ` x ) ) ) | 
						
							| 38 | 36 37 | sylan |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( ( bra ` A ) o. ( B ketbra C ) ) ` x ) = ( ( bra ` A ) ` ( ( B ketbra C ) ` x ) ) ) | 
						
							| 39 |  | kbval |  |-  ( ( B e. ~H /\ C e. ~H /\ x e. ~H ) -> ( ( B ketbra C ) ` x ) = ( ( x .ih C ) .h B ) ) | 
						
							| 40 | 18 21 22 39 | syl3anc |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( B ketbra C ) ` x ) = ( ( x .ih C ) .h B ) ) | 
						
							| 41 | 40 | fveq2d |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( bra ` A ) ` ( ( B ketbra C ) ` x ) ) = ( ( bra ` A ) ` ( ( x .ih C ) .h B ) ) ) | 
						
							| 42 |  | hvmulcl |  |-  ( ( ( x .ih C ) e. CC /\ B e. ~H ) -> ( ( x .ih C ) .h B ) e. ~H ) | 
						
							| 43 | 33 18 42 | syl2anc |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( x .ih C ) .h B ) e. ~H ) | 
						
							| 44 |  | braval |  |-  ( ( A e. ~H /\ ( ( x .ih C ) .h B ) e. ~H ) -> ( ( bra ` A ) ` ( ( x .ih C ) .h B ) ) = ( ( ( x .ih C ) .h B ) .ih A ) ) | 
						
							| 45 | 17 43 44 | syl2anc |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( bra ` A ) ` ( ( x .ih C ) .h B ) ) = ( ( ( x .ih C ) .h B ) .ih A ) ) | 
						
							| 46 | 38 41 45 | 3eqtrd |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( ( bra ` A ) o. ( B ketbra C ) ) ` x ) = ( ( ( x .ih C ) .h B ) .ih A ) ) | 
						
							| 47 | 27 33 | mulcomd |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( B .ih A ) x. ( x .ih C ) ) = ( ( x .ih C ) x. ( B .ih A ) ) ) | 
						
							| 48 | 35 46 47 | 3eqtr4d |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( ( bra ` A ) o. ( B ketbra C ) ) ` x ) = ( ( B .ih A ) x. ( x .ih C ) ) ) | 
						
							| 49 | 25 31 48 | 3eqtr4d |  |-  ( ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) /\ x e. ~H ) -> ( ( ( ( bra ` A ) ` B ) .fn ( bra ` C ) ) ` x ) = ( ( ( bra ` A ) o. ( B ketbra C ) ) ` x ) ) | 
						
							| 50 | 10 16 49 | eqfnfvd |  |-  ( ( A e. ~H /\ B e. ~H /\ C e. ~H ) -> ( ( ( bra ` A ) ` B ) .fn ( bra ` C ) ) = ( ( bra ` A ) o. ( B ketbra C ) ) ) |