| Step | Hyp | Ref | Expression | 
						
							| 1 |  | oveq2 |  |-  ( y = A -> ( ( x .ih z ) .h y ) = ( ( x .ih z ) .h A ) ) | 
						
							| 2 | 1 | mpteq2dv |  |-  ( y = A -> ( x e. ~H |-> ( ( x .ih z ) .h y ) ) = ( x e. ~H |-> ( ( x .ih z ) .h A ) ) ) | 
						
							| 3 |  | oveq2 |  |-  ( z = B -> ( x .ih z ) = ( x .ih B ) ) | 
						
							| 4 | 3 | oveq1d |  |-  ( z = B -> ( ( x .ih z ) .h A ) = ( ( x .ih B ) .h A ) ) | 
						
							| 5 | 4 | mpteq2dv |  |-  ( z = B -> ( x e. ~H |-> ( ( x .ih z ) .h A ) ) = ( x e. ~H |-> ( ( x .ih B ) .h A ) ) ) | 
						
							| 6 |  | df-kb |  |-  ketbra = ( y e. ~H , z e. ~H |-> ( x e. ~H |-> ( ( x .ih z ) .h y ) ) ) | 
						
							| 7 |  | ax-hilex |  |-  ~H e. _V | 
						
							| 8 | 7 | mptex |  |-  ( x e. ~H |-> ( ( x .ih B ) .h A ) ) e. _V | 
						
							| 9 | 2 5 6 8 | ovmpo |  |-  ( ( A e. ~H /\ B e. ~H ) -> ( A ketbra B ) = ( x e. ~H |-> ( ( x .ih B ) .h A ) ) ) |