| Step | Hyp | Ref | Expression | 
						
							| 1 |  | mdsymlem1.1 |  | 
						
							| 2 |  | mdsymlem1.2 |  | 
						
							| 3 |  | mdsymlem1.3 |  | 
						
							| 4 |  | ssin |  | 
						
							| 5 | 3 | sseq2i |  | 
						
							| 6 | 5 | biimpi |  | 
						
							| 7 | 6 | adantl |  | 
						
							| 8 | 4 7 | sylbir |  | 
						
							| 9 | 1 | atcvat4i |  | 
						
							| 10 | 9 | exp4b |  | 
						
							| 11 | 10 | com34 |  | 
						
							| 12 | 11 | com23 |  | 
						
							| 13 | 12 | imp4b |  | 
						
							| 14 | 8 13 | sylan2 |  | 
						
							| 15 | 14 | adantrr |  | 
						
							| 16 | 15 | com12 |  | 
						
							| 17 | 16 | adantlr |  | 
						
							| 18 | 17 | adantlr |  | 
						
							| 19 | 18 | imp |  | 
						
							| 20 |  | nssne2 |  | 
						
							| 21 | 20 | adantrl |  | 
						
							| 22 |  | atnemeq0 |  | 
						
							| 23 | 22 | ancoms |  | 
						
							| 24 | 21 23 | imbitrid |  | 
						
							| 25 | 24 | adantll |  | 
						
							| 26 | 25 | adantr |  | 
						
							| 27 |  | atelch |  | 
						
							| 28 |  | atelch |  | 
						
							| 29 |  | chjcom |  | 
						
							| 30 | 27 28 29 | syl2an |  | 
						
							| 31 | 30 | adantlr |  | 
						
							| 32 | 31 | sseq2d |  | 
						
							| 33 |  | atexch |  | 
						
							| 34 | 28 33 | syl3an1 |  | 
						
							| 35 | 34 | 3com13 |  | 
						
							| 36 | 35 | 3expa |  | 
						
							| 37 | 36 | expd |  | 
						
							| 38 | 32 37 | sylbid |  | 
						
							| 39 | 38 | imp |  | 
						
							| 40 | 26 39 | syld |  | 
						
							| 41 | 40 | expd |  | 
						
							| 42 | 41 | exp31 |  | 
						
							| 43 | 42 | com24 |  | 
						
							| 44 | 43 | impd |  | 
						
							| 45 | 44 | com24 |  | 
						
							| 46 | 45 | imp4b |  | 
						
							| 47 | 46 | anasss |  | 
						
							| 48 |  | simprl |  | 
						
							| 49 | 48 | a1i |  | 
						
							| 50 |  | simpl |  | 
						
							| 51 | 4 50 | sylbir |  | 
						
							| 52 | 51 | ad2antrl |  | 
						
							| 53 | 52 | adantl |  | 
						
							| 54 | 49 53 | jctird |  | 
						
							| 55 | 47 54 | jcad |  | 
						
							| 56 | 55 | expd |  | 
						
							| 57 | 56 | adantlr |  | 
						
							| 58 | 57 | adantlr |  | 
						
							| 59 | 58 | adantlr |  | 
						
							| 60 | 59 | reximdvai |  | 
						
							| 61 | 19 60 | mpd |  | 
						
							| 62 |  | chjcl |  | 
						
							| 63 | 1 62 | mpan |  | 
						
							| 64 | 3 63 | eqeltrid |  | 
						
							| 65 |  | chincl |  | 
						
							| 66 | 2 64 65 | sylancr |  | 
						
							| 67 | 27 66 | syl |  | 
						
							| 68 |  | chrelat2 |  | 
						
							| 69 | 67 1 68 | sylancl |  | 
						
							| 70 | 69 | biimpa |  | 
						
							| 71 | 70 | ad2antrr |  | 
						
							| 72 | 61 71 | reximddv |  |