| Step | Hyp | Ref | Expression | 
						
							| 1 |  | simpr | ⊢ ( ( ( 𝐵  ∈  ℕ0  ∧  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 ) )  ∧  𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) ) )  →  𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) ) ) | 
						
							| 2 |  | simplr | ⊢ ( ( ( 𝐵  ∈  ℕ0  ∧  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 ) )  ∧  𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) ) )  →  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 ) ) | 
						
							| 3 |  | ovex | ⊢ ( 1 ... 𝐴 )  ∈  V | 
						
							| 4 | 3 | mapco2 | ⊢ ( ( 𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) )  ∧  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 ) )  →  ( 𝑏  ∘  𝐹 )  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) ) ) | 
						
							| 5 | 1 2 4 | syl2anc | ⊢ ( ( ( 𝐵  ∈  ℕ0  ∧  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 ) )  ∧  𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) ) )  →  ( 𝑏  ∘  𝐹 )  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) ) ) | 
						
							| 6 | 5 | biantrurd | ⊢ ( ( ( 𝐵  ∈  ℕ0  ∧  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 ) )  ∧  𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) ) )  →  ( [ ( 𝑏  ∘  𝐹 )  /  𝑎 ] 𝜑  ↔  ( ( 𝑏  ∘  𝐹 )  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∧  [ ( 𝑏  ∘  𝐹 )  /  𝑎 ] 𝜑 ) ) ) | 
						
							| 7 |  | nfcv | ⊢ Ⅎ 𝑎 ( ℕ0  ↑m  ( 1 ... 𝐴 ) ) | 
						
							| 8 | 7 | elrabsf | ⊢ ( ( 𝑏  ∘  𝐹 )  ∈  { 𝑎  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∣  𝜑 }  ↔  ( ( 𝑏  ∘  𝐹 )  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∧  [ ( 𝑏  ∘  𝐹 )  /  𝑎 ] 𝜑 ) ) | 
						
							| 9 | 6 8 | bitr4di | ⊢ ( ( ( 𝐵  ∈  ℕ0  ∧  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 ) )  ∧  𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) ) )  →  ( [ ( 𝑏  ∘  𝐹 )  /  𝑎 ] 𝜑  ↔  ( 𝑏  ∘  𝐹 )  ∈  { 𝑎  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∣  𝜑 } ) ) | 
						
							| 10 | 9 | rabbidva | ⊢ ( ( 𝐵  ∈  ℕ0  ∧  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 ) )  →  { 𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) )  ∣  [ ( 𝑏  ∘  𝐹 )  /  𝑎 ] 𝜑 }  =  { 𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) )  ∣  ( 𝑏  ∘  𝐹 )  ∈  { 𝑎  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∣  𝜑 } } ) | 
						
							| 11 | 10 | 3adant3 | ⊢ ( ( 𝐵  ∈  ℕ0  ∧  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 )  ∧  { 𝑎  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∣  𝜑 }  ∈  ( Dioph ‘ 𝐴 ) )  →  { 𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) )  ∣  [ ( 𝑏  ∘  𝐹 )  /  𝑎 ] 𝜑 }  =  { 𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) )  ∣  ( 𝑏  ∘  𝐹 )  ∈  { 𝑎  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∣  𝜑 } } ) | 
						
							| 12 |  | diophren | ⊢ ( ( { 𝑎  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∣  𝜑 }  ∈  ( Dioph ‘ 𝐴 )  ∧  𝐵  ∈  ℕ0  ∧  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 ) )  →  { 𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) )  ∣  ( 𝑏  ∘  𝐹 )  ∈  { 𝑎  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∣  𝜑 } }  ∈  ( Dioph ‘ 𝐵 ) ) | 
						
							| 13 | 12 | 3coml | ⊢ ( ( 𝐵  ∈  ℕ0  ∧  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 )  ∧  { 𝑎  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∣  𝜑 }  ∈  ( Dioph ‘ 𝐴 ) )  →  { 𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) )  ∣  ( 𝑏  ∘  𝐹 )  ∈  { 𝑎  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∣  𝜑 } }  ∈  ( Dioph ‘ 𝐵 ) ) | 
						
							| 14 | 11 13 | eqeltrd | ⊢ ( ( 𝐵  ∈  ℕ0  ∧  𝐹 : ( 1 ... 𝐴 ) ⟶ ( 1 ... 𝐵 )  ∧  { 𝑎  ∈  ( ℕ0  ↑m  ( 1 ... 𝐴 ) )  ∣  𝜑 }  ∈  ( Dioph ‘ 𝐴 ) )  →  { 𝑏  ∈  ( ℕ0  ↑m  ( 1 ... 𝐵 ) )  ∣  [ ( 𝑏  ∘  𝐹 )  /  𝑎 ] 𝜑 }  ∈  ( Dioph ‘ 𝐵 ) ) |