| Step | Hyp | Ref | Expression | 
						
							| 1 |  | isirred2.1 | ⊢ 𝐵  =  ( Base ‘ 𝑅 ) | 
						
							| 2 |  | isirred2.2 | ⊢ 𝑈  =  ( Unit ‘ 𝑅 ) | 
						
							| 3 |  | isirred2.3 | ⊢ 𝐼  =  ( Irred ‘ 𝑅 ) | 
						
							| 4 |  | isirred2.4 | ⊢  ·   =  ( .r ‘ 𝑅 ) | 
						
							| 5 |  | eldif | ⊢ ( 𝑋  ∈  ( 𝐵  ∖  𝑈 )  ↔  ( 𝑋  ∈  𝐵  ∧  ¬  𝑋  ∈  𝑈 ) ) | 
						
							| 6 |  | eldif | ⊢ ( 𝑥  ∈  ( 𝐵  ∖  𝑈 )  ↔  ( 𝑥  ∈  𝐵  ∧  ¬  𝑥  ∈  𝑈 ) ) | 
						
							| 7 |  | eldif | ⊢ ( 𝑦  ∈  ( 𝐵  ∖  𝑈 )  ↔  ( 𝑦  ∈  𝐵  ∧  ¬  𝑦  ∈  𝑈 ) ) | 
						
							| 8 | 6 7 | anbi12i | ⊢ ( ( 𝑥  ∈  ( 𝐵  ∖  𝑈 )  ∧  𝑦  ∈  ( 𝐵  ∖  𝑈 ) )  ↔  ( ( 𝑥  ∈  𝐵  ∧  ¬  𝑥  ∈  𝑈 )  ∧  ( 𝑦  ∈  𝐵  ∧  ¬  𝑦  ∈  𝑈 ) ) ) | 
						
							| 9 |  | an4 | ⊢ ( ( ( 𝑥  ∈  𝐵  ∧  ¬  𝑥  ∈  𝑈 )  ∧  ( 𝑦  ∈  𝐵  ∧  ¬  𝑦  ∈  𝑈 ) )  ↔  ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  ∧  ( ¬  𝑥  ∈  𝑈  ∧  ¬  𝑦  ∈  𝑈 ) ) ) | 
						
							| 10 | 8 9 | bitri | ⊢ ( ( 𝑥  ∈  ( 𝐵  ∖  𝑈 )  ∧  𝑦  ∈  ( 𝐵  ∖  𝑈 ) )  ↔  ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  ∧  ( ¬  𝑥  ∈  𝑈  ∧  ¬  𝑦  ∈  𝑈 ) ) ) | 
						
							| 11 | 10 | imbi1i | ⊢ ( ( ( 𝑥  ∈  ( 𝐵  ∖  𝑈 )  ∧  𝑦  ∈  ( 𝐵  ∖  𝑈 ) )  →  ( 𝑥  ·  𝑦 )  ≠  𝑋 )  ↔  ( ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  ∧  ( ¬  𝑥  ∈  𝑈  ∧  ¬  𝑦  ∈  𝑈 ) )  →  ( 𝑥  ·  𝑦 )  ≠  𝑋 ) ) | 
						
							| 12 |  | impexp | ⊢ ( ( ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  ∧  ( ¬  𝑥  ∈  𝑈  ∧  ¬  𝑦  ∈  𝑈 ) )  →  ( 𝑥  ·  𝑦 )  ≠  𝑋 )  ↔  ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  →  ( ( ¬  𝑥  ∈  𝑈  ∧  ¬  𝑦  ∈  𝑈 )  →  ( 𝑥  ·  𝑦 )  ≠  𝑋 ) ) ) | 
						
							| 13 |  | pm4.56 | ⊢ ( ( ¬  𝑥  ∈  𝑈  ∧  ¬  𝑦  ∈  𝑈 )  ↔  ¬  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) | 
						
							| 14 |  | df-ne | ⊢ ( ( 𝑥  ·  𝑦 )  ≠  𝑋  ↔  ¬  ( 𝑥  ·  𝑦 )  =  𝑋 ) | 
						
							| 15 | 13 14 | imbi12i | ⊢ ( ( ( ¬  𝑥  ∈  𝑈  ∧  ¬  𝑦  ∈  𝑈 )  →  ( 𝑥  ·  𝑦 )  ≠  𝑋 )  ↔  ( ¬  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 )  →  ¬  ( 𝑥  ·  𝑦 )  =  𝑋 ) ) | 
						
							| 16 |  | con34b | ⊢ ( ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) )  ↔  ( ¬  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 )  →  ¬  ( 𝑥  ·  𝑦 )  =  𝑋 ) ) | 
						
							| 17 | 15 16 | bitr4i | ⊢ ( ( ( ¬  𝑥  ∈  𝑈  ∧  ¬  𝑦  ∈  𝑈 )  →  ( 𝑥  ·  𝑦 )  ≠  𝑋 )  ↔  ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) ) | 
						
							| 18 | 17 | imbi2i | ⊢ ( ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  →  ( ( ¬  𝑥  ∈  𝑈  ∧  ¬  𝑦  ∈  𝑈 )  →  ( 𝑥  ·  𝑦 )  ≠  𝑋 ) )  ↔  ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  →  ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) ) ) | 
						
							| 19 | 12 18 | bitri | ⊢ ( ( ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  ∧  ( ¬  𝑥  ∈  𝑈  ∧  ¬  𝑦  ∈  𝑈 ) )  →  ( 𝑥  ·  𝑦 )  ≠  𝑋 )  ↔  ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  →  ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) ) ) | 
						
							| 20 | 11 19 | bitri | ⊢ ( ( ( 𝑥  ∈  ( 𝐵  ∖  𝑈 )  ∧  𝑦  ∈  ( 𝐵  ∖  𝑈 ) )  →  ( 𝑥  ·  𝑦 )  ≠  𝑋 )  ↔  ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  →  ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) ) ) | 
						
							| 21 | 20 | 2albii | ⊢ ( ∀ 𝑥 ∀ 𝑦 ( ( 𝑥  ∈  ( 𝐵  ∖  𝑈 )  ∧  𝑦  ∈  ( 𝐵  ∖  𝑈 ) )  →  ( 𝑥  ·  𝑦 )  ≠  𝑋 )  ↔  ∀ 𝑥 ∀ 𝑦 ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  →  ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) ) ) | 
						
							| 22 |  | r2al | ⊢ ( ∀ 𝑥  ∈  ( 𝐵  ∖  𝑈 ) ∀ 𝑦  ∈  ( 𝐵  ∖  𝑈 ) ( 𝑥  ·  𝑦 )  ≠  𝑋  ↔  ∀ 𝑥 ∀ 𝑦 ( ( 𝑥  ∈  ( 𝐵  ∖  𝑈 )  ∧  𝑦  ∈  ( 𝐵  ∖  𝑈 ) )  →  ( 𝑥  ·  𝑦 )  ≠  𝑋 ) ) | 
						
							| 23 |  | r2al | ⊢ ( ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐵 ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) )  ↔  ∀ 𝑥 ∀ 𝑦 ( ( 𝑥  ∈  𝐵  ∧  𝑦  ∈  𝐵 )  →  ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) ) ) | 
						
							| 24 | 21 22 23 | 3bitr4i | ⊢ ( ∀ 𝑥  ∈  ( 𝐵  ∖  𝑈 ) ∀ 𝑦  ∈  ( 𝐵  ∖  𝑈 ) ( 𝑥  ·  𝑦 )  ≠  𝑋  ↔  ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐵 ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) ) | 
						
							| 25 | 5 24 | anbi12i | ⊢ ( ( 𝑋  ∈  ( 𝐵  ∖  𝑈 )  ∧  ∀ 𝑥  ∈  ( 𝐵  ∖  𝑈 ) ∀ 𝑦  ∈  ( 𝐵  ∖  𝑈 ) ( 𝑥  ·  𝑦 )  ≠  𝑋 )  ↔  ( ( 𝑋  ∈  𝐵  ∧  ¬  𝑋  ∈  𝑈 )  ∧  ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐵 ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) ) ) | 
						
							| 26 |  | eqid | ⊢ ( 𝐵  ∖  𝑈 )  =  ( 𝐵  ∖  𝑈 ) | 
						
							| 27 | 1 2 3 26 4 | isirred | ⊢ ( 𝑋  ∈  𝐼  ↔  ( 𝑋  ∈  ( 𝐵  ∖  𝑈 )  ∧  ∀ 𝑥  ∈  ( 𝐵  ∖  𝑈 ) ∀ 𝑦  ∈  ( 𝐵  ∖  𝑈 ) ( 𝑥  ·  𝑦 )  ≠  𝑋 ) ) | 
						
							| 28 |  | df-3an | ⊢ ( ( 𝑋  ∈  𝐵  ∧  ¬  𝑋  ∈  𝑈  ∧  ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐵 ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) )  ↔  ( ( 𝑋  ∈  𝐵  ∧  ¬  𝑋  ∈  𝑈 )  ∧  ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐵 ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) ) ) | 
						
							| 29 | 25 27 28 | 3bitr4i | ⊢ ( 𝑋  ∈  𝐼  ↔  ( 𝑋  ∈  𝐵  ∧  ¬  𝑋  ∈  𝑈  ∧  ∀ 𝑥  ∈  𝐵 ∀ 𝑦  ∈  𝐵 ( ( 𝑥  ·  𝑦 )  =  𝑋  →  ( 𝑥  ∈  𝑈  ∨  𝑦  ∈  𝑈 ) ) ) ) |