| Step | Hyp | Ref | Expression | 
						
							| 1 |  | mpteq12df.1 |  |-  F/ x ph | 
						
							| 2 |  | mpteq12df.2 |  |-  ( ph -> A = C ) | 
						
							| 3 |  | mpteq12df.3 |  |-  ( ph -> B = D ) | 
						
							| 4 |  | nfv |  |-  F/ y ph | 
						
							| 5 | 2 | eleq2d |  |-  ( ph -> ( x e. A <-> x e. C ) ) | 
						
							| 6 | 3 | eqeq2d |  |-  ( ph -> ( y = B <-> y = D ) ) | 
						
							| 7 | 5 6 | anbi12d |  |-  ( ph -> ( ( x e. A /\ y = B ) <-> ( x e. C /\ y = D ) ) ) | 
						
							| 8 | 1 4 7 | opabbid |  |-  ( ph -> { <. x , y >. | ( x e. A /\ y = B ) } = { <. x , y >. | ( x e. C /\ y = D ) } ) | 
						
							| 9 |  | df-mpt |  |-  ( x e. A |-> B ) = { <. x , y >. | ( x e. A /\ y = B ) } | 
						
							| 10 |  | df-mpt |  |-  ( x e. C |-> D ) = { <. x , y >. | ( x e. C /\ y = D ) } | 
						
							| 11 | 8 9 10 | 3eqtr4g |  |-  ( ph -> ( x e. A |-> B ) = ( x e. C |-> D ) ) |