| Step | Hyp | Ref | Expression | 
						
							| 1 |  | rzal | ⊢ ( 𝐴  =  ∅  →  ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐴 ( 𝜑  ∧  𝜓 ) ) | 
						
							| 2 |  | rzal | ⊢ ( 𝐴  =  ∅  →  ∀ 𝑥  ∈  𝐴 𝜑 ) | 
						
							| 3 |  | rzal | ⊢ ( 𝐴  =  ∅  →  ∀ 𝑦  ∈  𝐴 𝜓 ) | 
						
							| 4 |  | pm5.1 | ⊢ ( ( ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐴 ( 𝜑  ∧  𝜓 )  ∧  ( ∀ 𝑥  ∈  𝐴 𝜑  ∧  ∀ 𝑦  ∈  𝐴 𝜓 ) )  →  ( ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐴 ( 𝜑  ∧  𝜓 )  ↔  ( ∀ 𝑥  ∈  𝐴 𝜑  ∧  ∀ 𝑦  ∈  𝐴 𝜓 ) ) ) | 
						
							| 5 | 1 2 3 4 | syl12anc | ⊢ ( 𝐴  =  ∅  →  ( ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐴 ( 𝜑  ∧  𝜓 )  ↔  ( ∀ 𝑥  ∈  𝐴 𝜑  ∧  ∀ 𝑦  ∈  𝐴 𝜓 ) ) ) | 
						
							| 6 |  | r19.28zv | ⊢ ( 𝐴  ≠  ∅  →  ( ∀ 𝑦  ∈  𝐴 ( 𝜑  ∧  𝜓 )  ↔  ( 𝜑  ∧  ∀ 𝑦  ∈  𝐴 𝜓 ) ) ) | 
						
							| 7 | 6 | ralbidv | ⊢ ( 𝐴  ≠  ∅  →  ( ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐴 ( 𝜑  ∧  𝜓 )  ↔  ∀ 𝑥  ∈  𝐴 ( 𝜑  ∧  ∀ 𝑦  ∈  𝐴 𝜓 ) ) ) | 
						
							| 8 |  | r19.27zv | ⊢ ( 𝐴  ≠  ∅  →  ( ∀ 𝑥  ∈  𝐴 ( 𝜑  ∧  ∀ 𝑦  ∈  𝐴 𝜓 )  ↔  ( ∀ 𝑥  ∈  𝐴 𝜑  ∧  ∀ 𝑦  ∈  𝐴 𝜓 ) ) ) | 
						
							| 9 | 7 8 | bitrd | ⊢ ( 𝐴  ≠  ∅  →  ( ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐴 ( 𝜑  ∧  𝜓 )  ↔  ( ∀ 𝑥  ∈  𝐴 𝜑  ∧  ∀ 𝑦  ∈  𝐴 𝜓 ) ) ) | 
						
							| 10 | 5 9 | pm2.61ine | ⊢ ( ∀ 𝑥  ∈  𝐴 ∀ 𝑦  ∈  𝐴 ( 𝜑  ∧  𝜓 )  ↔  ( ∀ 𝑥  ∈  𝐴 𝜑  ∧  ∀ 𝑦  ∈  𝐴 𝜓 ) ) |