| Step | Hyp | Ref | Expression | 
						
							| 1 |  | dfoi.1 |  | 
						
							| 2 |  | dfoi.2 |  | 
						
							| 3 |  | dfoi.3 |  | 
						
							| 4 |  | df-oi |  | 
						
							| 5 | 1 | a1i |  | 
						
							| 6 | 5 | raleqdv |  | 
						
							| 7 | 5 6 | riotaeqbidv |  | 
						
							| 8 | 7 | mpteq2ia |  | 
						
							| 9 | 2 8 | eqtri |  | 
						
							| 10 |  | recseq |  | 
						
							| 11 | 9 10 | ax-mp |  | 
						
							| 12 | 3 11 | eqtri |  | 
						
							| 13 | 12 | imaeq1i |  | 
						
							| 14 | 13 | raleqi |  | 
						
							| 15 | 14 | rexbii |  | 
						
							| 16 | 15 | rabbii |  | 
						
							| 17 | 12 16 | reseq12i |  | 
						
							| 18 |  | ifeq1 |  | 
						
							| 19 | 17 18 | ax-mp |  | 
						
							| 20 | 4 19 | eqtr4i |  |