| Step | Hyp | Ref | Expression | 
						
							| 1 |  | df-ot |  |-  <. A , B , C >. = <. <. A , B >. , C >. | 
						
							| 2 |  | df-ot |  |-  <. D , E , F >. = <. <. D , E >. , F >. | 
						
							| 3 | 1 2 | eqeq12i |  |-  ( <. A , B , C >. = <. D , E , F >. <-> <. <. A , B >. , C >. = <. <. D , E >. , F >. ) | 
						
							| 4 |  | opex |  |-  <. A , B >. e. _V | 
						
							| 5 |  | opthg |  |-  ( ( <. A , B >. e. _V /\ C e. W ) -> ( <. <. A , B >. , C >. = <. <. D , E >. , F >. <-> ( <. A , B >. = <. D , E >. /\ C = F ) ) ) | 
						
							| 6 | 4 5 | mpan |  |-  ( C e. W -> ( <. <. A , B >. , C >. = <. <. D , E >. , F >. <-> ( <. A , B >. = <. D , E >. /\ C = F ) ) ) | 
						
							| 7 |  | opthg |  |-  ( ( A e. U /\ B e. V ) -> ( <. A , B >. = <. D , E >. <-> ( A = D /\ B = E ) ) ) | 
						
							| 8 | 7 | anbi1d |  |-  ( ( A e. U /\ B e. V ) -> ( ( <. A , B >. = <. D , E >. /\ C = F ) <-> ( ( A = D /\ B = E ) /\ C = F ) ) ) | 
						
							| 9 |  | df-3an |  |-  ( ( A = D /\ B = E /\ C = F ) <-> ( ( A = D /\ B = E ) /\ C = F ) ) | 
						
							| 10 | 8 9 | bitr4di |  |-  ( ( A e. U /\ B e. V ) -> ( ( <. A , B >. = <. D , E >. /\ C = F ) <-> ( A = D /\ B = E /\ C = F ) ) ) | 
						
							| 11 | 6 10 | sylan9bbr |  |-  ( ( ( A e. U /\ B e. V ) /\ C e. W ) -> ( <. <. A , B >. , C >. = <. <. D , E >. , F >. <-> ( A = D /\ B = E /\ C = F ) ) ) | 
						
							| 12 | 11 | 3impa |  |-  ( ( A e. U /\ B e. V /\ C e. W ) -> ( <. <. A , B >. , C >. = <. <. D , E >. , F >. <-> ( A = D /\ B = E /\ C = F ) ) ) | 
						
							| 13 | 3 12 | bitrid |  |-  ( ( A e. U /\ B e. V /\ C e. W ) -> ( <. A , B , C >. = <. D , E , F >. <-> ( A = D /\ B = E /\ C = F ) ) ) |