| Step | Hyp | Ref | Expression | 
						
							| 1 |  | isofrlem.1 |  | 
						
							| 2 |  | isofrlem.2 |  | 
						
							| 3 |  | dfse2 |  | 
						
							| 4 | 3 | biimpi |  | 
						
							| 5 | 4 | r19.21bi |  | 
						
							| 6 | 5 | expcom |  | 
						
							| 7 | 6 | adantl |  | 
						
							| 8 |  | imaeq2 |  | 
						
							| 9 | 8 | eleq1d |  | 
						
							| 10 | 9 | imbi2d |  | 
						
							| 11 | 10 2 | vtoclg |  | 
						
							| 12 | 11 | com12 |  | 
						
							| 13 | 12 | adantr |  | 
						
							| 14 |  | isoini |  | 
						
							| 15 | 1 14 | sylan |  | 
						
							| 16 | 15 | eleq1d |  | 
						
							| 17 | 13 16 | sylibd |  | 
						
							| 18 | 7 17 | syld |  | 
						
							| 19 | 18 | ralrimdva |  | 
						
							| 20 |  | isof1o |  | 
						
							| 21 |  | f1ofn |  | 
						
							| 22 |  | sneq |  | 
						
							| 23 | 22 | imaeq2d |  | 
						
							| 24 | 23 | ineq2d |  | 
						
							| 25 | 24 | eleq1d |  | 
						
							| 26 | 25 | ralrn |  | 
						
							| 27 | 1 20 21 26 | 4syl |  | 
						
							| 28 |  | f1ofo |  | 
						
							| 29 |  | forn |  | 
						
							| 30 | 1 20 28 29 | 4syl |  | 
						
							| 31 | 30 | raleqdv |  | 
						
							| 32 | 27 31 | bitr3d |  | 
						
							| 33 | 19 32 | sylibd |  | 
						
							| 34 |  | dfse2 |  | 
						
							| 35 | 33 34 | imbitrrdi |  |