| Step | Hyp | Ref | Expression | 
						
							| 1 |  | elntg.1 |  | 
						
							| 2 |  | elntg.2 |  | 
						
							| 3 |  | lngid |  | 
						
							| 4 |  | fvex |  | 
						
							| 5 | 4 | a1i |  | 
						
							| 6 |  | eengstr |  | 
						
							| 7 |  | structn0fun |  | 
						
							| 8 | 6 7 | syl |  | 
						
							| 9 |  | structcnvcnv |  | 
						
							| 10 | 6 9 | syl |  | 
						
							| 11 | 10 | funeqd |  | 
						
							| 12 | 8 11 | mpbird |  | 
						
							| 13 |  | opex |  | 
						
							| 14 | 13 | prid2 |  | 
						
							| 15 |  | elun2 |  | 
						
							| 16 | 14 15 | ax-mp |  | 
						
							| 17 |  | eengv |  | 
						
							| 18 | 16 17 | eleqtrrid |  | 
						
							| 19 |  | fvex |  | 
						
							| 20 | 19 | difexi |  | 
						
							| 21 | 19 20 | mpoex |  | 
						
							| 22 | 21 | a1i |  | 
						
							| 23 | 3 5 12 18 22 | strfv2d |  | 
						
							| 24 |  | eengbas |  | 
						
							| 25 | 24 1 | eqtr4di |  | 
						
							| 26 | 25 | difeq1d |  | 
						
							| 27 | 26 | adantr |  | 
						
							| 28 | 25 | adantr |  | 
						
							| 29 |  | simpll |  | 
						
							| 30 |  | simplrl |  | 
						
							| 31 | 29 25 | syl |  | 
						
							| 32 | 30 31 | eleqtrd |  | 
						
							| 33 |  | simplrr |  | 
						
							| 34 | 33 | eldifad |  | 
						
							| 35 | 34 31 | eleqtrd |  | 
						
							| 36 |  | simpr |  | 
						
							| 37 | 36 31 | eleqtrd |  | 
						
							| 38 | 29 1 2 32 35 37 | ebtwntg |  | 
						
							| 39 | 29 1 2 37 35 32 | ebtwntg |  | 
						
							| 40 | 29 1 2 32 37 35 | ebtwntg |  | 
						
							| 41 | 38 39 40 | 3orbi123d |  | 
						
							| 42 | 28 41 | rabeqbidva |  | 
						
							| 43 | 25 27 42 | mpoeq123dva |  | 
						
							| 44 | 23 43 | eqtr3d |  |