| Step | Hyp | Ref | Expression | 
						
							| 1 |  | simprr | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  𝐶  =  ∪  ◡ { 𝐵 } ) | 
						
							| 2 |  | 1st2nd | ⊢ ( ( Rel  𝐴  ∧  𝐵  ∈  𝐴 )  →  𝐵  =  〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉 ) | 
						
							| 3 | 2 | adantrr | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  𝐵  =  〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉 ) | 
						
							| 4 | 3 | sneqd | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  { 𝐵 }  =  { 〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉 } ) | 
						
							| 5 | 4 | cnveqd | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  ◡ { 𝐵 }  =  ◡ { 〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉 } ) | 
						
							| 6 | 5 | unieqd | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  ∪  ◡ { 𝐵 }  =  ∪  ◡ { 〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉 } ) | 
						
							| 7 | 1 6 | eqtrd | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  𝐶  =  ∪  ◡ { 〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉 } ) | 
						
							| 8 |  | opswap | ⊢ ∪  ◡ { 〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉 }  =  〈 ( 2nd  ‘ 𝐵 ) ,  ( 1st  ‘ 𝐵 ) 〉 | 
						
							| 9 | 7 8 | eqtrdi | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  𝐶  =  〈 ( 2nd  ‘ 𝐵 ) ,  ( 1st  ‘ 𝐵 ) 〉 ) | 
						
							| 10 |  | simprl | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  𝐵  ∈  𝐴 ) | 
						
							| 11 | 3 10 | eqeltrrd | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉  ∈  𝐴 ) | 
						
							| 12 |  | fvex | ⊢ ( 2nd  ‘ 𝐵 )  ∈  V | 
						
							| 13 |  | fvex | ⊢ ( 1st  ‘ 𝐵 )  ∈  V | 
						
							| 14 | 12 13 | opelcnv | ⊢ ( 〈 ( 2nd  ‘ 𝐵 ) ,  ( 1st  ‘ 𝐵 ) 〉  ∈  ◡ 𝐴  ↔  〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉  ∈  𝐴 ) | 
						
							| 15 | 11 14 | sylibr | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  〈 ( 2nd  ‘ 𝐵 ) ,  ( 1st  ‘ 𝐵 ) 〉  ∈  ◡ 𝐴 ) | 
						
							| 16 | 9 15 | eqeltrd | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  𝐶  ∈  ◡ 𝐴 ) | 
						
							| 17 |  | opswap | ⊢ ∪  ◡ { 〈 ( 2nd  ‘ 𝐵 ) ,  ( 1st  ‘ 𝐵 ) 〉 }  =  〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉 | 
						
							| 18 | 17 | eqcomi | ⊢ 〈 ( 1st  ‘ 𝐵 ) ,  ( 2nd  ‘ 𝐵 ) 〉  =  ∪  ◡ { 〈 ( 2nd  ‘ 𝐵 ) ,  ( 1st  ‘ 𝐵 ) 〉 } | 
						
							| 19 | 9 | sneqd | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  { 𝐶 }  =  { 〈 ( 2nd  ‘ 𝐵 ) ,  ( 1st  ‘ 𝐵 ) 〉 } ) | 
						
							| 20 | 19 | cnveqd | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  ◡ { 𝐶 }  =  ◡ { 〈 ( 2nd  ‘ 𝐵 ) ,  ( 1st  ‘ 𝐵 ) 〉 } ) | 
						
							| 21 | 20 | unieqd | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  ∪  ◡ { 𝐶 }  =  ∪  ◡ { 〈 ( 2nd  ‘ 𝐵 ) ,  ( 1st  ‘ 𝐵 ) 〉 } ) | 
						
							| 22 | 18 3 21 | 3eqtr4a | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  𝐵  =  ∪  ◡ { 𝐶 } ) | 
						
							| 23 | 16 22 | jca | ⊢ ( ( Rel  𝐴  ∧  ( 𝐵  ∈  𝐴  ∧  𝐶  =  ∪  ◡ { 𝐵 } ) )  →  ( 𝐶  ∈  ◡ 𝐴  ∧  𝐵  =  ∪  ◡ { 𝐶 } ) ) |