| Step | Hyp | Ref | Expression | 
						
							| 1 |  | comfeqval.b |  |-  B = ( Base ` C ) | 
						
							| 2 |  | comfeqval.h |  |-  H = ( Hom ` C ) | 
						
							| 3 |  | comfeqval.1 |  |-  .x. = ( comp ` C ) | 
						
							| 4 |  | comfeqval.2 |  |-  .xb = ( comp ` D ) | 
						
							| 5 |  | comfeqval.3 |  |-  ( ph -> ( Homf ` C ) = ( Homf ` D ) ) | 
						
							| 6 |  | comfeqval.4 |  |-  ( ph -> ( comf ` C ) = ( comf ` D ) ) | 
						
							| 7 |  | comfeqval.x |  |-  ( ph -> X e. B ) | 
						
							| 8 |  | comfeqval.y |  |-  ( ph -> Y e. B ) | 
						
							| 9 |  | comfeqval.z |  |-  ( ph -> Z e. B ) | 
						
							| 10 |  | comfeqval.f |  |-  ( ph -> F e. ( X H Y ) ) | 
						
							| 11 |  | comfeqval.g |  |-  ( ph -> G e. ( Y H Z ) ) | 
						
							| 12 | 6 | oveqd |  |-  ( ph -> ( <. X , Y >. ( comf ` C ) Z ) = ( <. X , Y >. ( comf ` D ) Z ) ) | 
						
							| 13 | 12 | oveqd |  |-  ( ph -> ( G ( <. X , Y >. ( comf ` C ) Z ) F ) = ( G ( <. X , Y >. ( comf ` D ) Z ) F ) ) | 
						
							| 14 |  | eqid |  |-  ( comf ` C ) = ( comf ` C ) | 
						
							| 15 | 14 1 2 3 7 8 9 10 11 | comfval |  |-  ( ph -> ( G ( <. X , Y >. ( comf ` C ) Z ) F ) = ( G ( <. X , Y >. .x. Z ) F ) ) | 
						
							| 16 |  | eqid |  |-  ( comf ` D ) = ( comf ` D ) | 
						
							| 17 |  | eqid |  |-  ( Base ` D ) = ( Base ` D ) | 
						
							| 18 |  | eqid |  |-  ( Hom ` D ) = ( Hom ` D ) | 
						
							| 19 | 5 | homfeqbas |  |-  ( ph -> ( Base ` C ) = ( Base ` D ) ) | 
						
							| 20 | 1 19 | eqtrid |  |-  ( ph -> B = ( Base ` D ) ) | 
						
							| 21 | 7 20 | eleqtrd |  |-  ( ph -> X e. ( Base ` D ) ) | 
						
							| 22 | 8 20 | eleqtrd |  |-  ( ph -> Y e. ( Base ` D ) ) | 
						
							| 23 | 9 20 | eleqtrd |  |-  ( ph -> Z e. ( Base ` D ) ) | 
						
							| 24 | 1 2 18 5 7 8 | homfeqval |  |-  ( ph -> ( X H Y ) = ( X ( Hom ` D ) Y ) ) | 
						
							| 25 | 10 24 | eleqtrd |  |-  ( ph -> F e. ( X ( Hom ` D ) Y ) ) | 
						
							| 26 | 1 2 18 5 8 9 | homfeqval |  |-  ( ph -> ( Y H Z ) = ( Y ( Hom ` D ) Z ) ) | 
						
							| 27 | 11 26 | eleqtrd |  |-  ( ph -> G e. ( Y ( Hom ` D ) Z ) ) | 
						
							| 28 | 16 17 18 4 21 22 23 25 27 | comfval |  |-  ( ph -> ( G ( <. X , Y >. ( comf ` D ) Z ) F ) = ( G ( <. X , Y >. .xb Z ) F ) ) | 
						
							| 29 | 13 15 28 | 3eqtr3d |  |-  ( ph -> ( G ( <. X , Y >. .x. Z ) F ) = ( G ( <. X , Y >. .xb Z ) F ) ) |