| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							preq12bg | 
							⊢ ( ( ( 𝐴  ∈  𝑈  ∧  𝐵  ∈  𝑉 )  ∧  ( 𝐶  ∈  𝑋  ∧  𝐷  ∈  𝑌 ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  ↔  ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  ∨  ( 𝐴  =  𝐷  ∧  𝐵  =  𝐶 ) ) ) )  | 
						
						
							| 2 | 
							
								
							 | 
							orddi | 
							⊢ ( ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  ∨  ( 𝐴  =  𝐷  ∧  𝐵  =  𝐶 ) )  ↔  ( ( ( 𝐴  =  𝐶  ∨  𝐴  =  𝐷 )  ∧  ( 𝐴  =  𝐶  ∨  𝐵  =  𝐶 ) )  ∧  ( ( 𝐵  =  𝐷  ∨  𝐴  =  𝐷 )  ∧  ( 𝐵  =  𝐷  ∨  𝐵  =  𝐶 ) ) ) )  | 
						
						
							| 3 | 
							
								
							 | 
							simpll | 
							⊢ ( ( ( ( 𝐴  =  𝐶  ∨  𝐴  =  𝐷 )  ∧  ( 𝐴  =  𝐶  ∨  𝐵  =  𝐶 ) )  ∧  ( ( 𝐵  =  𝐷  ∨  𝐴  =  𝐷 )  ∧  ( 𝐵  =  𝐷  ∨  𝐵  =  𝐶 ) ) )  →  ( 𝐴  =  𝐶  ∨  𝐴  =  𝐷 ) )  | 
						
						
							| 4 | 
							
								
							 | 
							pm1.4 | 
							⊢ ( ( 𝐵  =  𝐷  ∨  𝐵  =  𝐶 )  →  ( 𝐵  =  𝐶  ∨  𝐵  =  𝐷 ) )  | 
						
						
							| 5 | 
							
								4
							 | 
							ad2antll | 
							⊢ ( ( ( ( 𝐴  =  𝐶  ∨  𝐴  =  𝐷 )  ∧  ( 𝐴  =  𝐶  ∨  𝐵  =  𝐶 ) )  ∧  ( ( 𝐵  =  𝐷  ∨  𝐴  =  𝐷 )  ∧  ( 𝐵  =  𝐷  ∨  𝐵  =  𝐶 ) ) )  →  ( 𝐵  =  𝐶  ∨  𝐵  =  𝐷 ) )  | 
						
						
							| 6 | 
							
								3 5
							 | 
							jca | 
							⊢ ( ( ( ( 𝐴  =  𝐶  ∨  𝐴  =  𝐷 )  ∧  ( 𝐴  =  𝐶  ∨  𝐵  =  𝐶 ) )  ∧  ( ( 𝐵  =  𝐷  ∨  𝐴  =  𝐷 )  ∧  ( 𝐵  =  𝐷  ∨  𝐵  =  𝐶 ) ) )  →  ( ( 𝐴  =  𝐶  ∨  𝐴  =  𝐷 )  ∧  ( 𝐵  =  𝐶  ∨  𝐵  =  𝐷 ) ) )  | 
						
						
							| 7 | 
							
								2 6
							 | 
							sylbi | 
							⊢ ( ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  ∨  ( 𝐴  =  𝐷  ∧  𝐵  =  𝐶 ) )  →  ( ( 𝐴  =  𝐶  ∨  𝐴  =  𝐷 )  ∧  ( 𝐵  =  𝐶  ∨  𝐵  =  𝐷 ) ) )  | 
						
						
							| 8 | 
							
								1 7
							 | 
							biimtrdi | 
							⊢ ( ( ( 𝐴  ∈  𝑈  ∧  𝐵  ∈  𝑉 )  ∧  ( 𝐶  ∈  𝑋  ∧  𝐷  ∈  𝑌 ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  →  ( ( 𝐴  =  𝐶  ∨  𝐴  =  𝐷 )  ∧  ( 𝐵  =  𝐶  ∨  𝐵  =  𝐷 ) ) ) )  | 
						
						
							| 9 | 
							
								
							 | 
							ianor | 
							⊢ ( ¬  ( 𝐴  ≠  𝐶  ∧  𝐴  ≠  𝐷 )  ↔  ( ¬  𝐴  ≠  𝐶  ∨  ¬  𝐴  ≠  𝐷 ) )  | 
						
						
							| 10 | 
							
								
							 | 
							nne | 
							⊢ ( ¬  𝐴  ≠  𝐶  ↔  𝐴  =  𝐶 )  | 
						
						
							| 11 | 
							
								
							 | 
							nne | 
							⊢ ( ¬  𝐴  ≠  𝐷  ↔  𝐴  =  𝐷 )  | 
						
						
							| 12 | 
							
								10 11
							 | 
							orbi12i | 
							⊢ ( ( ¬  𝐴  ≠  𝐶  ∨  ¬  𝐴  ≠  𝐷 )  ↔  ( 𝐴  =  𝐶  ∨  𝐴  =  𝐷 ) )  | 
						
						
							| 13 | 
							
								9 12
							 | 
							bitr2i | 
							⊢ ( ( 𝐴  =  𝐶  ∨  𝐴  =  𝐷 )  ↔  ¬  ( 𝐴  ≠  𝐶  ∧  𝐴  ≠  𝐷 ) )  | 
						
						
							| 14 | 
							
								
							 | 
							ianor | 
							⊢ ( ¬  ( 𝐵  ≠  𝐶  ∧  𝐵  ≠  𝐷 )  ↔  ( ¬  𝐵  ≠  𝐶  ∨  ¬  𝐵  ≠  𝐷 ) )  | 
						
						
							| 15 | 
							
								
							 | 
							nne | 
							⊢ ( ¬  𝐵  ≠  𝐶  ↔  𝐵  =  𝐶 )  | 
						
						
							| 16 | 
							
								
							 | 
							nne | 
							⊢ ( ¬  𝐵  ≠  𝐷  ↔  𝐵  =  𝐷 )  | 
						
						
							| 17 | 
							
								15 16
							 | 
							orbi12i | 
							⊢ ( ( ¬  𝐵  ≠  𝐶  ∨  ¬  𝐵  ≠  𝐷 )  ↔  ( 𝐵  =  𝐶  ∨  𝐵  =  𝐷 ) )  | 
						
						
							| 18 | 
							
								14 17
							 | 
							bitr2i | 
							⊢ ( ( 𝐵  =  𝐶  ∨  𝐵  =  𝐷 )  ↔  ¬  ( 𝐵  ≠  𝐶  ∧  𝐵  ≠  𝐷 ) )  | 
						
						
							| 19 | 
							
								13 18
							 | 
							anbi12i | 
							⊢ ( ( ( 𝐴  =  𝐶  ∨  𝐴  =  𝐷 )  ∧  ( 𝐵  =  𝐶  ∨  𝐵  =  𝐷 ) )  ↔  ( ¬  ( 𝐴  ≠  𝐶  ∧  𝐴  ≠  𝐷 )  ∧  ¬  ( 𝐵  ≠  𝐶  ∧  𝐵  ≠  𝐷 ) ) )  | 
						
						
							| 20 | 
							
								8 19
							 | 
							imbitrdi | 
							⊢ ( ( ( 𝐴  ∈  𝑈  ∧  𝐵  ∈  𝑉 )  ∧  ( 𝐶  ∈  𝑋  ∧  𝐷  ∈  𝑌 ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  →  ( ¬  ( 𝐴  ≠  𝐶  ∧  𝐴  ≠  𝐷 )  ∧  ¬  ( 𝐵  ≠  𝐶  ∧  𝐵  ≠  𝐷 ) ) ) )  | 
						
						
							| 21 | 
							
								
							 | 
							pm4.56 | 
							⊢ ( ( ¬  ( 𝐴  ≠  𝐶  ∧  𝐴  ≠  𝐷 )  ∧  ¬  ( 𝐵  ≠  𝐶  ∧  𝐵  ≠  𝐷 ) )  ↔  ¬  ( ( 𝐴  ≠  𝐶  ∧  𝐴  ≠  𝐷 )  ∨  ( 𝐵  ≠  𝐶  ∧  𝐵  ≠  𝐷 ) ) )  | 
						
						
							| 22 | 
							
								20 21
							 | 
							imbitrdi | 
							⊢ ( ( ( 𝐴  ∈  𝑈  ∧  𝐵  ∈  𝑉 )  ∧  ( 𝐶  ∈  𝑋  ∧  𝐷  ∈  𝑌 ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  →  ¬  ( ( 𝐴  ≠  𝐶  ∧  𝐴  ≠  𝐷 )  ∨  ( 𝐵  ≠  𝐶  ∧  𝐵  ≠  𝐷 ) ) ) )  | 
						
						
							| 23 | 
							
								22
							 | 
							necon2ad | 
							⊢ ( ( ( 𝐴  ∈  𝑈  ∧  𝐵  ∈  𝑉 )  ∧  ( 𝐶  ∈  𝑋  ∧  𝐷  ∈  𝑌 ) )  →  ( ( ( 𝐴  ≠  𝐶  ∧  𝐴  ≠  𝐷 )  ∨  ( 𝐵  ≠  𝐶  ∧  𝐵  ≠  𝐷 ) )  →  { 𝐴 ,  𝐵 }  ≠  { 𝐶 ,  𝐷 } ) )  |