| Step | Hyp | Ref | Expression | 
						
							| 1 |  | imaeqexov.1 | ⊢ ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  ( 𝜑  ↔  𝜓 ) ) | 
						
							| 2 |  | df-ral | ⊢ ( ∀ 𝑥  ∈  ( 𝐹  “  ( 𝐵  ×  𝐶 ) ) 𝜑  ↔  ∀ 𝑥 ( 𝑥  ∈  ( 𝐹  “  ( 𝐵  ×  𝐶 ) )  →  𝜑 ) ) | 
						
							| 3 |  | ovelimab | ⊢ ( ( 𝐹  Fn  𝐴  ∧  ( 𝐵  ×  𝐶 )  ⊆  𝐴 )  →  ( 𝑥  ∈  ( 𝐹  “  ( 𝐵  ×  𝐶 ) )  ↔  ∃ 𝑦  ∈  𝐵 ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 ) ) ) | 
						
							| 4 | 3 | imbi1d | ⊢ ( ( 𝐹  Fn  𝐴  ∧  ( 𝐵  ×  𝐶 )  ⊆  𝐴 )  →  ( ( 𝑥  ∈  ( 𝐹  “  ( 𝐵  ×  𝐶 ) )  →  𝜑 )  ↔  ( ∃ 𝑦  ∈  𝐵 ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 ) ) ) | 
						
							| 5 | 4 | albidv | ⊢ ( ( 𝐹  Fn  𝐴  ∧  ( 𝐵  ×  𝐶 )  ⊆  𝐴 )  →  ( ∀ 𝑥 ( 𝑥  ∈  ( 𝐹  “  ( 𝐵  ×  𝐶 ) )  →  𝜑 )  ↔  ∀ 𝑥 ( ∃ 𝑦  ∈  𝐵 ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 ) ) ) | 
						
							| 6 | 2 5 | bitrid | ⊢ ( ( 𝐹  Fn  𝐴  ∧  ( 𝐵  ×  𝐶 )  ⊆  𝐴 )  →  ( ∀ 𝑥  ∈  ( 𝐹  “  ( 𝐵  ×  𝐶 ) ) 𝜑  ↔  ∀ 𝑥 ( ∃ 𝑦  ∈  𝐵 ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 ) ) ) | 
						
							| 7 |  | ralcom4 | ⊢ ( ∀ 𝑦  ∈  𝐵 ∀ 𝑥 ∀ 𝑧  ∈  𝐶 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ∀ 𝑥 ∀ 𝑦  ∈  𝐵 ∀ 𝑧  ∈  𝐶 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 ) ) | 
						
							| 8 |  | r19.23v | ⊢ ( ∀ 𝑧  ∈  𝐶 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ( ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 ) ) | 
						
							| 9 | 8 | ralbii | ⊢ ( ∀ 𝑦  ∈  𝐵 ∀ 𝑧  ∈  𝐶 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ∀ 𝑦  ∈  𝐵 ( ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 ) ) | 
						
							| 10 |  | r19.23v | ⊢ ( ∀ 𝑦  ∈  𝐵 ( ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ( ∃ 𝑦  ∈  𝐵 ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 ) ) | 
						
							| 11 | 9 10 | bitri | ⊢ ( ∀ 𝑦  ∈  𝐵 ∀ 𝑧  ∈  𝐶 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ( ∃ 𝑦  ∈  𝐵 ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 ) ) | 
						
							| 12 | 11 | albii | ⊢ ( ∀ 𝑥 ∀ 𝑦  ∈  𝐵 ∀ 𝑧  ∈  𝐶 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ∀ 𝑥 ( ∃ 𝑦  ∈  𝐵 ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 ) ) | 
						
							| 13 | 7 12 | bitri | ⊢ ( ∀ 𝑦  ∈  𝐵 ∀ 𝑥 ∀ 𝑧  ∈  𝐶 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ∀ 𝑥 ( ∃ 𝑦  ∈  𝐵 ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 ) ) | 
						
							| 14 |  | ralcom4 | ⊢ ( ∀ 𝑧  ∈  𝐶 ∀ 𝑥 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ∀ 𝑥 ∀ 𝑧  ∈  𝐶 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 ) ) | 
						
							| 15 |  | ovex | ⊢ ( 𝑦 𝐹 𝑧 )  ∈  V | 
						
							| 16 | 15 1 | ceqsalv | ⊢ ( ∀ 𝑥 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  𝜓 ) | 
						
							| 17 | 16 | ralbii | ⊢ ( ∀ 𝑧  ∈  𝐶 ∀ 𝑥 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ∀ 𝑧  ∈  𝐶 𝜓 ) | 
						
							| 18 | 14 17 | bitr3i | ⊢ ( ∀ 𝑥 ∀ 𝑧  ∈  𝐶 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ∀ 𝑧  ∈  𝐶 𝜓 ) | 
						
							| 19 | 18 | ralbii | ⊢ ( ∀ 𝑦  ∈  𝐵 ∀ 𝑥 ∀ 𝑧  ∈  𝐶 ( 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ∀ 𝑦  ∈  𝐵 ∀ 𝑧  ∈  𝐶 𝜓 ) | 
						
							| 20 | 13 19 | bitr3i | ⊢ ( ∀ 𝑥 ( ∃ 𝑦  ∈  𝐵 ∃ 𝑧  ∈  𝐶 𝑥  =  ( 𝑦 𝐹 𝑧 )  →  𝜑 )  ↔  ∀ 𝑦  ∈  𝐵 ∀ 𝑧  ∈  𝐶 𝜓 ) | 
						
							| 21 | 6 20 | bitrdi | ⊢ ( ( 𝐹  Fn  𝐴  ∧  ( 𝐵  ×  𝐶 )  ⊆  𝐴 )  →  ( ∀ 𝑥  ∈  ( 𝐹  “  ( 𝐵  ×  𝐶 ) ) 𝜑  ↔  ∀ 𝑦  ∈  𝐵 ∀ 𝑧  ∈  𝐶 𝜓 ) ) |