| Step | Hyp | Ref | Expression | 
						
							| 1 |  | 1st2nd2 | ⊢ ( 𝐴  ∈  ( 𝐶  ×  𝐷 )  →  𝐴  =  〈 ( 1st  ‘ 𝐴 ) ,  ( 2nd  ‘ 𝐴 ) 〉 ) | 
						
							| 2 |  | 1st2nd2 | ⊢ ( 𝐵  ∈  ( 𝑅  ×  𝑆 )  →  𝐵  =  〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉 ) | 
						
							| 3 | 1 2 | eqeqan12d | ⊢ ( ( 𝐴  ∈  ( 𝐶  ×  𝐷 )  ∧  𝐵  ∈  ( 𝑅  ×  𝑆 ) )  →  ( 𝐴  =  𝐵  ↔  〈 ( 1st  ‘ 𝐴 ) ,  ( 2nd  ‘ 𝐴 ) 〉  =  〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉 ) ) | 
						
							| 4 |  | fvex | ⊢ ( 1st  ‘ 𝐴 )  ∈  V | 
						
							| 5 |  | fvex | ⊢ ( 2nd  ‘ 𝐴 )  ∈  V | 
						
							| 6 | 4 5 | opth | ⊢ ( 〈 ( 1st  ‘ 𝐴 ) ,  ( 2nd  ‘ 𝐴 ) 〉  =  〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉  ↔  ( ( 1st  ‘ 𝐴 )  =  ( 1st  ‘ 𝐵 )  ∧  ( 2nd  ‘ 𝐴 )  =  ( 2nd  ‘ 𝐵 ) ) ) | 
						
							| 7 | 3 6 | bitr2di | ⊢ ( ( 𝐴  ∈  ( 𝐶  ×  𝐷 )  ∧  𝐵  ∈  ( 𝑅  ×  𝑆 ) )  →  ( ( ( 1st  ‘ 𝐴 )  =  ( 1st  ‘ 𝐵 )  ∧  ( 2nd  ‘ 𝐴 )  =  ( 2nd  ‘ 𝐵 ) )  ↔  𝐴  =  𝐵 ) ) |