| Step | Hyp | Ref | Expression | 
						
							| 1 |  | preq12bg | ⊢ ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐶  ∈  V  ∧  𝐷  ∈  V ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  ↔  ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  ∨  ( 𝐴  =  𝐷  ∧  𝐵  =  𝐶 ) ) ) ) | 
						
							| 2 | 1 | adantlr | ⊢ ( ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) )  ∧  ( 𝐶  ∈  V  ∧  𝐷  ∈  V ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  ↔  ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  ∨  ( 𝐴  =  𝐷  ∧  𝐵  =  𝐶 ) ) ) ) | 
						
							| 3 |  | idd | ⊢ ( 𝐴  ≠  𝐷  →  ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  →  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 4 |  | df-ne | ⊢ ( 𝐴  ≠  𝐷  ↔  ¬  𝐴  =  𝐷 ) | 
						
							| 5 |  | pm2.21 | ⊢ ( ¬  𝐴  =  𝐷  →  ( 𝐴  =  𝐷  →  ( 𝐵  =  𝐶  →  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) ) | 
						
							| 6 | 4 5 | sylbi | ⊢ ( 𝐴  ≠  𝐷  →  ( 𝐴  =  𝐷  →  ( 𝐵  =  𝐶  →  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) ) | 
						
							| 7 | 6 | impd | ⊢ ( 𝐴  ≠  𝐷  →  ( ( 𝐴  =  𝐷  ∧  𝐵  =  𝐶 )  →  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 8 | 3 7 | jaod | ⊢ ( 𝐴  ≠  𝐷  →  ( ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  ∨  ( 𝐴  =  𝐷  ∧  𝐵  =  𝐶 ) )  →  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 9 |  | orc | ⊢ ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  →  ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  ∨  ( 𝐴  =  𝐷  ∧  𝐵  =  𝐶 ) ) ) | 
						
							| 10 | 8 9 | impbid1 | ⊢ ( 𝐴  ≠  𝐷  →  ( ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  ∨  ( 𝐴  =  𝐷  ∧  𝐵  =  𝐶 ) )  ↔  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 11 | 10 | adantl | ⊢ ( ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 )  →  ( ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  ∨  ( 𝐴  =  𝐷  ∧  𝐵  =  𝐶 ) )  ↔  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 12 | 11 | ad2antlr | ⊢ ( ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) )  ∧  ( 𝐶  ∈  V  ∧  𝐷  ∈  V ) )  →  ( ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  ∨  ( 𝐴  =  𝐷  ∧  𝐵  =  𝐶 ) )  ↔  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 13 | 2 12 | bitrd | ⊢ ( ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) )  ∧  ( 𝐶  ∈  V  ∧  𝐷  ∈  V ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  ↔  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 14 | 13 | expcom | ⊢ ( ( 𝐶  ∈  V  ∧  𝐷  ∈  V )  →  ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  ↔  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) ) | 
						
							| 15 |  | ianor | ⊢ ( ¬  ( 𝐶  ∈  V  ∧  𝐷  ∈  V )  ↔  ( ¬  𝐶  ∈  V  ∨  ¬  𝐷  ∈  V ) ) | 
						
							| 16 |  | simpl | ⊢ ( ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 )  →  𝐴  ≠  𝐵 ) | 
						
							| 17 | 16 | anim2i | ⊢ ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) )  →  ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  𝐴  ≠  𝐵 ) ) | 
						
							| 18 |  | df-3an | ⊢ ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊  ∧  𝐴  ≠  𝐵 )  ↔  ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  𝐴  ≠  𝐵 ) ) | 
						
							| 19 | 17 18 | sylibr | ⊢ ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) )  →  ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊  ∧  𝐴  ≠  𝐵 ) ) | 
						
							| 20 |  | prneprprc | ⊢ ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊  ∧  𝐴  ≠  𝐵 )  ∧  ¬  𝐶  ∈  V )  →  { 𝐴 ,  𝐵 }  ≠  { 𝐶 ,  𝐷 } ) | 
						
							| 21 | 19 20 | sylan | ⊢ ( ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) )  ∧  ¬  𝐶  ∈  V )  →  { 𝐴 ,  𝐵 }  ≠  { 𝐶 ,  𝐷 } ) | 
						
							| 22 | 21 | ancoms | ⊢ ( ( ¬  𝐶  ∈  V  ∧  ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) ) )  →  { 𝐴 ,  𝐵 }  ≠  { 𝐶 ,  𝐷 } ) | 
						
							| 23 |  | eqneqall | ⊢ ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  →  ( { 𝐴 ,  𝐵 }  ≠  { 𝐶 ,  𝐷 }  →  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 24 | 22 23 | syl5com | ⊢ ( ( ¬  𝐶  ∈  V  ∧  ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  →  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 25 |  | prneprprc | ⊢ ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊  ∧  𝐴  ≠  𝐵 )  ∧  ¬  𝐷  ∈  V )  →  { 𝐴 ,  𝐵 }  ≠  { 𝐷 ,  𝐶 } ) | 
						
							| 26 | 19 25 | sylan | ⊢ ( ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) )  ∧  ¬  𝐷  ∈  V )  →  { 𝐴 ,  𝐵 }  ≠  { 𝐷 ,  𝐶 } ) | 
						
							| 27 | 26 | ancoms | ⊢ ( ( ¬  𝐷  ∈  V  ∧  ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) ) )  →  { 𝐴 ,  𝐵 }  ≠  { 𝐷 ,  𝐶 } ) | 
						
							| 28 |  | prcom | ⊢ { 𝐶 ,  𝐷 }  =  { 𝐷 ,  𝐶 } | 
						
							| 29 | 28 | eqeq2i | ⊢ ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  ↔  { 𝐴 ,  𝐵 }  =  { 𝐷 ,  𝐶 } ) | 
						
							| 30 |  | eqneqall | ⊢ ( { 𝐴 ,  𝐵 }  =  { 𝐷 ,  𝐶 }  →  ( { 𝐴 ,  𝐵 }  ≠  { 𝐷 ,  𝐶 }  →  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 31 | 29 30 | sylbi | ⊢ ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  →  ( { 𝐴 ,  𝐵 }  ≠  { 𝐷 ,  𝐶 }  →  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 32 | 27 31 | syl5com | ⊢ ( ( ¬  𝐷  ∈  V  ∧  ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  →  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 33 | 24 32 | jaoian | ⊢ ( ( ( ¬  𝐶  ∈  V  ∨  ¬  𝐷  ∈  V )  ∧  ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  →  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 34 |  | preq12 | ⊢ ( ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 )  →  { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 } ) | 
						
							| 35 | 33 34 | impbid1 | ⊢ ( ( ( ¬  𝐶  ∈  V  ∨  ¬  𝐷  ∈  V )  ∧  ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  ↔  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) | 
						
							| 36 | 35 | ex | ⊢ ( ( ¬  𝐶  ∈  V  ∨  ¬  𝐷  ∈  V )  →  ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  ↔  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) ) | 
						
							| 37 | 15 36 | sylbi | ⊢ ( ¬  ( 𝐶  ∈  V  ∧  𝐷  ∈  V )  →  ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  ↔  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) ) | 
						
							| 38 | 14 37 | pm2.61i | ⊢ ( ( ( 𝐴  ∈  𝑉  ∧  𝐵  ∈  𝑊 )  ∧  ( 𝐴  ≠  𝐵  ∧  𝐴  ≠  𝐷 ) )  →  ( { 𝐴 ,  𝐵 }  =  { 𝐶 ,  𝐷 }  ↔  ( 𝐴  =  𝐶  ∧  𝐵  =  𝐷 ) ) ) |