| Step | Hyp | Ref
| Expression |
| 1 | | peano2nc 6146 |
. . . 4
 NC 
1c
NC  |
| 2 | | dflec2 6211 |
. . . 4
  NC  1c NC  c  1c  NC 
1c
     |
| 3 | 1, 2 | sylan2 460 |
. . 3
  NC NC  c 
1c
 NC 
1c
     |
| 4 | | nc0suc 6218 |
. . . . 5
 NC  0c 
NC  1c   |
| 5 | | addceq2 4385 |
. . . . . . . . . 10
 0c  
 0c  |
| 6 | | addcid1 4406 |
. . . . . . . . . 10
 0c
 |
| 7 | 5, 6 | syl6eq 2401 |
. . . . . . . . 9
 0c  
  |
| 8 | 7 | eqeq2d 2364 |
. . . . . . . 8
 0c   1c   
1c
   |
| 9 | | olc 373 |
. . . . . . . . 9
  1c  c
 1c   |
| 10 | 9 | eqcoms 2356 |
. . . . . . . 8
 
1c
 c
 1c   |
| 11 | 8, 10 | syl6bi 219 |
. . . . . . 7
 0c   1c    c  1c    |
| 12 | 11 | a1i 10 |
. . . . . 6
  NC NC  0c   1c    c  1c     |
| 13 | | addceq2 4385 |
. . . . . . . . . . . 12
  1c  
 
1c   |
| 14 | | addcass 4416 |
. . . . . . . . . . . 12
   1c
 
1c  |
| 15 | 13, 14 | syl6eqr 2403 |
. . . . . . . . . . 11
  1c  
   1c  |
| 16 | 15 | eqeq2d 2364 |
. . . . . . . . . 10
  1c   1c   
1c
 
 1c   |
| 17 | 16 | biimpa 470 |
. . . . . . . . 9
   1c  1c   
 1c    1c  |
| 18 | | simplr 731 |
. . . . . . . . . . 11
   NC NC NC
NC  |
| 19 | | ncaddccl 6145 |
. . . . . . . . . . . 12
  NC NC   NC  |
| 20 | 19 | adantlr 695 |
. . . . . . . . . . 11
   NC NC NC 

NC  |
| 21 | | peano4nc 6151 |
. . . . . . . . . . 11
  NC  
NC  
1c
 
 1c      |
| 22 | 18, 20, 21 | syl2anc 642 |
. . . . . . . . . 10
   NC NC NC  
1c
 
 1c      |
| 23 | | addlecncs 6210 |
. . . . . . . . . . . . 13
  NC NC c     |
| 24 | 23 | adantlr 695 |
. . . . . . . . . . . 12
   NC NC NC c     |
| 25 | | breq2 4644 |
. . . . . . . . . . . 12
  
 c c      |
| 26 | 24, 25 | syl5ibrcom 213 |
. . . . . . . . . . 11
   NC NC NC 
  c    |
| 27 | | orc 374 |
. . . . . . . . . . 11
 c  c 
1c   |
| 28 | 26, 27 | syl6 29 |
. . . . . . . . . 10
   NC NC NC 
  
c
 1c    |
| 29 | 22, 28 | sylbid 206 |
. . . . . . . . 9
   NC NC NC  
1c
 
 1c  c 
1c    |
| 30 | 17, 29 | syl5 28 |
. . . . . . . 8
   NC NC NC   
1c
 1c    
c
 1c    |
| 31 | 30 | exp3a 425 |
. . . . . . 7
   NC NC NC 
 1c  
1c
  
c
 1c     |
| 32 | 31 | rexlimdva 2739 |
. . . . . 6
  NC NC  
NC  1c   1c
   c 
1c     |
| 33 | 12, 32 | jaod 369 |
. . . . 5
  NC NC  
0c  NC 
1c  
1c
  
c
 1c     |
| 34 | 4, 33 | syl5 28 |
. . . 4
  NC NC  NC   1c    c  1c     |
| 35 | 34 | rexlimdv 2738 |
. . 3
  NC NC  
NC 
1c
  
c
 1c    |
| 36 | 3, 35 | sylbid 206 |
. 2
  NC NC  c 
1c
 c 
1c    |
| 37 | | 1cnc 6140 |
. . . . . 6
1c
NC |
| 38 | | addlecncs 6210 |
. . . . . 6
  NC 1c NC c  1c  |
| 39 | 37, 38 | mpan2 652 |
. . . . 5
 NC c 
1c  |
| 40 | 39 | adantl 452 |
. . . 4
  NC NC c 
1c  |
| 41 | 1 | adantl 452 |
. . . . 5
  NC NC  1c
NC  |
| 42 | | lectr 6212 |
. . . . 5
  NC NC  1c NC   c c 
1c c 
1c   |
| 43 | 41, 42 | mpd3an3 1278 |
. . . 4
  NC NC   c c 
1c c 
1c   |
| 44 | 40, 43 | mpan2d 655 |
. . 3
  NC NC  c c 
1c   |
| 45 | | nclecid 6198 |
. . . . . 6
 
1c
NC  1c c 
1c  |
| 46 | 1, 45 | syl 15 |
. . . . 5
 NC 
1c
c  1c  |
| 47 | 46 | adantl 452 |
. . . 4
  NC NC  1c c 
1c  |
| 48 | | breq1 4643 |
. . . 4
  1c  c  1c 
1c
c  1c   |
| 49 | 47, 48 | syl5ibrcom 213 |
. . 3
  NC NC   1c c 
1c   |
| 50 | 44, 49 | jaod 369 |
. 2
  NC NC   c 
1c c 
1c   |
| 51 | 36, 50 | impbid 183 |
1
  NC NC  c 
1c
 c 
1c    |