| Step | Hyp | Ref | Expression | 
						
							| 1 |  | elex |  | 
						
							| 2 | 1 | adantr |  | 
						
							| 3 |  | elex |  | 
						
							| 4 | 3 | adantl |  | 
						
							| 5 |  | funmpt |  | 
						
							| 6 | 5 | a1i |  | 
						
							| 7 |  | dftpos4 |  | 
						
							| 8 |  | tposexg |  | 
						
							| 9 | 8 | adantr |  | 
						
							| 10 | 7 9 | eqeltrrid |  | 
						
							| 11 |  | dftpos4 |  | 
						
							| 12 |  | tposexg |  | 
						
							| 13 | 12 | adantl |  | 
						
							| 14 | 11 13 | eqeltrrid |  | 
						
							| 15 |  | ofco2 |  | 
						
							| 16 | 2 4 6 10 14 15 | syl23anc |  | 
						
							| 17 |  | dftpos4 |  | 
						
							| 18 | 7 11 | oveq12i |  | 
						
							| 19 | 16 17 18 | 3eqtr4g |  |