| Step | Hyp | Ref | Expression | 
						
							| 1 |  | upwlksfval.v |  | 
						
							| 2 |  | upwlksfval.i |  | 
						
							| 3 | 1 2 | upwlksfval |  | 
						
							| 4 | 3 | brfvopab |  | 
						
							| 5 | 4 | a1i |  | 
						
							| 6 |  | elex |  | 
						
							| 7 |  | elex |  | 
						
							| 8 |  | ovex |  | 
						
							| 9 | 1 | fvexi |  | 
						
							| 10 | 8 9 | fpm |  | 
						
							| 11 | 10 | elexd |  | 
						
							| 12 | 7 11 | anim12i |  | 
						
							| 13 | 12 | 3adant3 |  | 
						
							| 14 | 6 13 | anim12i |  | 
						
							| 15 | 14 | ex |  | 
						
							| 16 |  | 3anass |  | 
						
							| 17 | 15 16 | imbitrrdi |  | 
						
							| 18 | 1 2 | isupwlk |  | 
						
							| 19 | 18 | a1i |  | 
						
							| 20 | 5 17 19 | pm5.21ndd |  |