| Step | Hyp | Ref | Expression | 
						
							| 1 |  | poleloe |  |-  ( C e. X -> ( B ( R u. _I ) C <-> ( B R C \/ B = C ) ) ) | 
						
							| 2 | 1 | 3ad2ant3 |  |-  ( ( A e. X /\ B e. X /\ C e. X ) -> ( B ( R u. _I ) C <-> ( B R C \/ B = C ) ) ) | 
						
							| 3 | 2 | adantl |  |-  ( ( R Po X /\ ( A e. X /\ B e. X /\ C e. X ) ) -> ( B ( R u. _I ) C <-> ( B R C \/ B = C ) ) ) | 
						
							| 4 | 3 | anbi2d |  |-  ( ( R Po X /\ ( A e. X /\ B e. X /\ C e. X ) ) -> ( ( A R B /\ B ( R u. _I ) C ) <-> ( A R B /\ ( B R C \/ B = C ) ) ) ) | 
						
							| 5 |  | potr |  |-  ( ( R Po X /\ ( A e. X /\ B e. X /\ C e. X ) ) -> ( ( A R B /\ B R C ) -> A R C ) ) | 
						
							| 6 | 5 | com12 |  |-  ( ( A R B /\ B R C ) -> ( ( R Po X /\ ( A e. X /\ B e. X /\ C e. X ) ) -> A R C ) ) | 
						
							| 7 |  | breq2 |  |-  ( B = C -> ( A R B <-> A R C ) ) | 
						
							| 8 | 7 | biimpac |  |-  ( ( A R B /\ B = C ) -> A R C ) | 
						
							| 9 | 8 | a1d |  |-  ( ( A R B /\ B = C ) -> ( ( R Po X /\ ( A e. X /\ B e. X /\ C e. X ) ) -> A R C ) ) | 
						
							| 10 | 6 9 | jaodan |  |-  ( ( A R B /\ ( B R C \/ B = C ) ) -> ( ( R Po X /\ ( A e. X /\ B e. X /\ C e. X ) ) -> A R C ) ) | 
						
							| 11 | 10 | com12 |  |-  ( ( R Po X /\ ( A e. X /\ B e. X /\ C e. X ) ) -> ( ( A R B /\ ( B R C \/ B = C ) ) -> A R C ) ) | 
						
							| 12 | 4 11 | sylbid |  |-  ( ( R Po X /\ ( A e. X /\ B e. X /\ C e. X ) ) -> ( ( A R B /\ B ( R u. _I ) C ) -> A R C ) ) |