| Step | Hyp | Ref | Expression | 
						
							| 1 |  | brco3f1o.c | ⊢ ( 𝜑  →  𝐶 : 𝑌 –1-1-onto→ 𝑍 ) | 
						
							| 2 |  | brco3f1o.d | ⊢ ( 𝜑  →  𝐷 : 𝑋 –1-1-onto→ 𝑌 ) | 
						
							| 3 |  | brco3f1o.e | ⊢ ( 𝜑  →  𝐸 : 𝑊 –1-1-onto→ 𝑋 ) | 
						
							| 4 |  | brco3f1o.r | ⊢ ( 𝜑  →  𝐴 ( 𝐶  ∘  ( 𝐷  ∘  𝐸 ) ) 𝐵 ) | 
						
							| 5 |  | f1ocnv | ⊢ ( 𝐸 : 𝑊 –1-1-onto→ 𝑋  →  ◡ 𝐸 : 𝑋 –1-1-onto→ 𝑊 ) | 
						
							| 6 |  | f1ofn | ⊢ ( ◡ 𝐸 : 𝑋 –1-1-onto→ 𝑊  →  ◡ 𝐸  Fn  𝑋 ) | 
						
							| 7 | 3 5 6 | 3syl | ⊢ ( 𝜑  →  ◡ 𝐸  Fn  𝑋 ) | 
						
							| 8 |  | f1ocnv | ⊢ ( 𝐷 : 𝑋 –1-1-onto→ 𝑌  →  ◡ 𝐷 : 𝑌 –1-1-onto→ 𝑋 ) | 
						
							| 9 |  | f1of | ⊢ ( ◡ 𝐷 : 𝑌 –1-1-onto→ 𝑋  →  ◡ 𝐷 : 𝑌 ⟶ 𝑋 ) | 
						
							| 10 | 2 8 9 | 3syl | ⊢ ( 𝜑  →  ◡ 𝐷 : 𝑌 ⟶ 𝑋 ) | 
						
							| 11 |  | f1ocnv | ⊢ ( 𝐶 : 𝑌 –1-1-onto→ 𝑍  →  ◡ 𝐶 : 𝑍 –1-1-onto→ 𝑌 ) | 
						
							| 12 |  | f1of | ⊢ ( ◡ 𝐶 : 𝑍 –1-1-onto→ 𝑌  →  ◡ 𝐶 : 𝑍 ⟶ 𝑌 ) | 
						
							| 13 | 1 11 12 | 3syl | ⊢ ( 𝜑  →  ◡ 𝐶 : 𝑍 ⟶ 𝑌 ) | 
						
							| 14 |  | relco | ⊢ Rel  ( ( 𝐶  ∘  𝐷 )  ∘  𝐸 ) | 
						
							| 15 | 14 | relbrcnv | ⊢ ( 𝐵 ◡ ( ( 𝐶  ∘  𝐷 )  ∘  𝐸 ) 𝐴  ↔  𝐴 ( ( 𝐶  ∘  𝐷 )  ∘  𝐸 ) 𝐵 ) | 
						
							| 16 |  | cnvco | ⊢ ◡ ( ( 𝐶  ∘  𝐷 )  ∘  𝐸 )  =  ( ◡ 𝐸  ∘  ◡ ( 𝐶  ∘  𝐷 ) ) | 
						
							| 17 |  | cnvco | ⊢ ◡ ( 𝐶  ∘  𝐷 )  =  ( ◡ 𝐷  ∘  ◡ 𝐶 ) | 
						
							| 18 | 17 | coeq2i | ⊢ ( ◡ 𝐸  ∘  ◡ ( 𝐶  ∘  𝐷 ) )  =  ( ◡ 𝐸  ∘  ( ◡ 𝐷  ∘  ◡ 𝐶 ) ) | 
						
							| 19 | 16 18 | eqtri | ⊢ ◡ ( ( 𝐶  ∘  𝐷 )  ∘  𝐸 )  =  ( ◡ 𝐸  ∘  ( ◡ 𝐷  ∘  ◡ 𝐶 ) ) | 
						
							| 20 | 19 | breqi | ⊢ ( 𝐵 ◡ ( ( 𝐶  ∘  𝐷 )  ∘  𝐸 ) 𝐴  ↔  𝐵 ( ◡ 𝐸  ∘  ( ◡ 𝐷  ∘  ◡ 𝐶 ) ) 𝐴 ) | 
						
							| 21 |  | coass | ⊢ ( ( 𝐶  ∘  𝐷 )  ∘  𝐸 )  =  ( 𝐶  ∘  ( 𝐷  ∘  𝐸 ) ) | 
						
							| 22 | 21 | breqi | ⊢ ( 𝐴 ( ( 𝐶  ∘  𝐷 )  ∘  𝐸 ) 𝐵  ↔  𝐴 ( 𝐶  ∘  ( 𝐷  ∘  𝐸 ) ) 𝐵 ) | 
						
							| 23 | 15 20 22 | 3bitr3ri | ⊢ ( 𝐴 ( 𝐶  ∘  ( 𝐷  ∘  𝐸 ) ) 𝐵  ↔  𝐵 ( ◡ 𝐸  ∘  ( ◡ 𝐷  ∘  ◡ 𝐶 ) ) 𝐴 ) | 
						
							| 24 | 4 23 | sylib | ⊢ ( 𝜑  →  𝐵 ( ◡ 𝐸  ∘  ( ◡ 𝐷  ∘  ◡ 𝐶 ) ) 𝐴 ) | 
						
							| 25 | 7 10 13 24 | brcofffn | ⊢ ( 𝜑  →  ( 𝐵 ◡ 𝐶 ( ◡ 𝐶 ‘ 𝐵 )  ∧  ( ◡ 𝐶 ‘ 𝐵 ) ◡ 𝐷 ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) )  ∧  ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) ◡ 𝐸 𝐴 ) ) | 
						
							| 26 |  | f1orel | ⊢ ( 𝐶 : 𝑌 –1-1-onto→ 𝑍  →  Rel  𝐶 ) | 
						
							| 27 |  | relbrcnvg | ⊢ ( Rel  𝐶  →  ( 𝐵 ◡ 𝐶 ( ◡ 𝐶 ‘ 𝐵 )  ↔  ( ◡ 𝐶 ‘ 𝐵 ) 𝐶 𝐵 ) ) | 
						
							| 28 | 1 26 27 | 3syl | ⊢ ( 𝜑  →  ( 𝐵 ◡ 𝐶 ( ◡ 𝐶 ‘ 𝐵 )  ↔  ( ◡ 𝐶 ‘ 𝐵 ) 𝐶 𝐵 ) ) | 
						
							| 29 |  | f1orel | ⊢ ( 𝐷 : 𝑋 –1-1-onto→ 𝑌  →  Rel  𝐷 ) | 
						
							| 30 |  | relbrcnvg | ⊢ ( Rel  𝐷  →  ( ( ◡ 𝐶 ‘ 𝐵 ) ◡ 𝐷 ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) )  ↔  ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) 𝐷 ( ◡ 𝐶 ‘ 𝐵 ) ) ) | 
						
							| 31 | 2 29 30 | 3syl | ⊢ ( 𝜑  →  ( ( ◡ 𝐶 ‘ 𝐵 ) ◡ 𝐷 ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) )  ↔  ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) 𝐷 ( ◡ 𝐶 ‘ 𝐵 ) ) ) | 
						
							| 32 |  | f1orel | ⊢ ( 𝐸 : 𝑊 –1-1-onto→ 𝑋  →  Rel  𝐸 ) | 
						
							| 33 |  | relbrcnvg | ⊢ ( Rel  𝐸  →  ( ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) ◡ 𝐸 𝐴  ↔  𝐴 𝐸 ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) ) ) | 
						
							| 34 | 3 32 33 | 3syl | ⊢ ( 𝜑  →  ( ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) ◡ 𝐸 𝐴  ↔  𝐴 𝐸 ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) ) ) | 
						
							| 35 | 28 31 34 | 3anbi123d | ⊢ ( 𝜑  →  ( ( 𝐵 ◡ 𝐶 ( ◡ 𝐶 ‘ 𝐵 )  ∧  ( ◡ 𝐶 ‘ 𝐵 ) ◡ 𝐷 ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) )  ∧  ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) ◡ 𝐸 𝐴 )  ↔  ( ( ◡ 𝐶 ‘ 𝐵 ) 𝐶 𝐵  ∧  ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) 𝐷 ( ◡ 𝐶 ‘ 𝐵 )  ∧  𝐴 𝐸 ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) ) ) ) | 
						
							| 36 | 25 35 | mpbid | ⊢ ( 𝜑  →  ( ( ◡ 𝐶 ‘ 𝐵 ) 𝐶 𝐵  ∧  ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) 𝐷 ( ◡ 𝐶 ‘ 𝐵 )  ∧  𝐴 𝐸 ( ◡ 𝐷 ‘ ( ◡ 𝐶 ‘ 𝐵 ) ) ) ) |