| Step | Hyp | Ref | Expression | 
						
							| 1 |  | comfeqval.b | ⊢ 𝐵  =  ( Base ‘ 𝐶 ) | 
						
							| 2 |  | comfeqval.h | ⊢ 𝐻  =  ( Hom  ‘ 𝐶 ) | 
						
							| 3 |  | comfeqval.1 | ⊢  ·   =  ( comp ‘ 𝐶 ) | 
						
							| 4 |  | comfeqval.2 | ⊢  ∙   =  ( comp ‘ 𝐷 ) | 
						
							| 5 |  | comfeqval.3 | ⊢ ( 𝜑  →  ( Homf  ‘ 𝐶 )  =  ( Homf  ‘ 𝐷 ) ) | 
						
							| 6 |  | comfeqval.4 | ⊢ ( 𝜑  →  ( compf ‘ 𝐶 )  =  ( compf ‘ 𝐷 ) ) | 
						
							| 7 |  | comfeqval.x | ⊢ ( 𝜑  →  𝑋  ∈  𝐵 ) | 
						
							| 8 |  | comfeqval.y | ⊢ ( 𝜑  →  𝑌  ∈  𝐵 ) | 
						
							| 9 |  | comfeqval.z | ⊢ ( 𝜑  →  𝑍  ∈  𝐵 ) | 
						
							| 10 |  | comfeqval.f | ⊢ ( 𝜑  →  𝐹  ∈  ( 𝑋 𝐻 𝑌 ) ) | 
						
							| 11 |  | comfeqval.g | ⊢ ( 𝜑  →  𝐺  ∈  ( 𝑌 𝐻 𝑍 ) ) | 
						
							| 12 | 6 | oveqd | ⊢ ( 𝜑  →  ( 〈 𝑋 ,  𝑌 〉 ( compf ‘ 𝐶 ) 𝑍 )  =  ( 〈 𝑋 ,  𝑌 〉 ( compf ‘ 𝐷 ) 𝑍 ) ) | 
						
							| 13 | 12 | oveqd | ⊢ ( 𝜑  →  ( 𝐺 ( 〈 𝑋 ,  𝑌 〉 ( compf ‘ 𝐶 ) 𝑍 ) 𝐹 )  =  ( 𝐺 ( 〈 𝑋 ,  𝑌 〉 ( compf ‘ 𝐷 ) 𝑍 ) 𝐹 ) ) | 
						
							| 14 |  | eqid | ⊢ ( compf ‘ 𝐶 )  =  ( compf ‘ 𝐶 ) | 
						
							| 15 | 14 1 2 3 7 8 9 10 11 | comfval | ⊢ ( 𝜑  →  ( 𝐺 ( 〈 𝑋 ,  𝑌 〉 ( compf ‘ 𝐶 ) 𝑍 ) 𝐹 )  =  ( 𝐺 ( 〈 𝑋 ,  𝑌 〉  ·  𝑍 ) 𝐹 ) ) | 
						
							| 16 |  | eqid | ⊢ ( compf ‘ 𝐷 )  =  ( compf ‘ 𝐷 ) | 
						
							| 17 |  | eqid | ⊢ ( Base ‘ 𝐷 )  =  ( Base ‘ 𝐷 ) | 
						
							| 18 |  | eqid | ⊢ ( Hom  ‘ 𝐷 )  =  ( Hom  ‘ 𝐷 ) | 
						
							| 19 | 5 | homfeqbas | ⊢ ( 𝜑  →  ( Base ‘ 𝐶 )  =  ( Base ‘ 𝐷 ) ) | 
						
							| 20 | 1 19 | eqtrid | ⊢ ( 𝜑  →  𝐵  =  ( Base ‘ 𝐷 ) ) | 
						
							| 21 | 7 20 | eleqtrd | ⊢ ( 𝜑  →  𝑋  ∈  ( Base ‘ 𝐷 ) ) | 
						
							| 22 | 8 20 | eleqtrd | ⊢ ( 𝜑  →  𝑌  ∈  ( Base ‘ 𝐷 ) ) | 
						
							| 23 | 9 20 | eleqtrd | ⊢ ( 𝜑  →  𝑍  ∈  ( Base ‘ 𝐷 ) ) | 
						
							| 24 | 1 2 18 5 7 8 | homfeqval | ⊢ ( 𝜑  →  ( 𝑋 𝐻 𝑌 )  =  ( 𝑋 ( Hom  ‘ 𝐷 ) 𝑌 ) ) | 
						
							| 25 | 10 24 | eleqtrd | ⊢ ( 𝜑  →  𝐹  ∈  ( 𝑋 ( Hom  ‘ 𝐷 ) 𝑌 ) ) | 
						
							| 26 | 1 2 18 5 8 9 | homfeqval | ⊢ ( 𝜑  →  ( 𝑌 𝐻 𝑍 )  =  ( 𝑌 ( Hom  ‘ 𝐷 ) 𝑍 ) ) | 
						
							| 27 | 11 26 | eleqtrd | ⊢ ( 𝜑  →  𝐺  ∈  ( 𝑌 ( Hom  ‘ 𝐷 ) 𝑍 ) ) | 
						
							| 28 | 16 17 18 4 21 22 23 25 27 | comfval | ⊢ ( 𝜑  →  ( 𝐺 ( 〈 𝑋 ,  𝑌 〉 ( compf ‘ 𝐷 ) 𝑍 ) 𝐹 )  =  ( 𝐺 ( 〈 𝑋 ,  𝑌 〉  ∙  𝑍 ) 𝐹 ) ) | 
						
							| 29 | 13 15 28 | 3eqtr3d | ⊢ ( 𝜑  →  ( 𝐺 ( 〈 𝑋 ,  𝑌 〉  ·  𝑍 ) 𝐹 )  =  ( 𝐺 ( 〈 𝑋 ,  𝑌 〉  ∙  𝑍 ) 𝐹 ) ) |