| Step | Hyp | Ref
 | Expression | 
| 1 |   | peano2nc 6146 | 
. . . . . 6
       NC       
1c 
  NC   | 
| 2 | 1 | adantr 451 | 
. . . . 5
        NC       NC          1c   
NC   | 
| 3 | 2 | adantr 451 | 
. . . 4
         NC       NC          1c   
     1c  
       1c    NC   | 
| 4 |   | elncs 6120 | 
. . . . 5
       
1c 
  NC          1c   
Nc    | 
| 5 |   | simpr 447 | 
. . . . . . . . 9
        
1c 
       1c         1c   
Nc           1c    Nc    | 
| 6 |   | eqtr2 2371 | 
. . . . . . . . 9
        
1c 
       1c         1c   
Nc           1c    Nc    | 
| 7 | 5, 6 | jca 518 | 
. . . . . . . 8
        
1c 
       1c         1c   
Nc         
 
1c 
  Nc          1c   
Nc     | 
| 8 |   | vex 2863 | 
. . . . . . . . . . . . . 14
        | 
| 9 | 8 | ncid 6124 | 
. . . . . . . . . . . . 13
      Nc   | 
| 10 |   | eleq2 2414 | 
. . . . . . . . . . . . 13
       
1c 
  Nc               1c       
Nc     | 
| 11 | 9, 10 | mpbiri 224 | 
. . . . . . . . . . . 12
       
1c 
  Nc             
1c   | 
| 12 |   | elsuc 4414 | 
. . . . . . . . . . . . 13
            1c      
      
  ∼                 | 
| 13 | 12 | biimpi 186 | 
. . . . . . . . . . . 12
            1c             
  ∼                 | 
| 14 | 11, 13 | syl 15 | 
. . . . . . . . . . 11
       
1c 
  Nc                 ∼   
             | 
| 15 |   | eleq2 2414 | 
. . . . . . . . . . . . 13
       
1c 
  Nc               1c       
Nc     | 
| 16 | 9, 15 | mpbiri 224 | 
. . . . . . . . . . . 12
       
1c 
  Nc             
1c   | 
| 17 |   | elsuc 4414 | 
. . . . . . . . . . . 12
            1c      
      
  ∼                 | 
| 18 | 16, 17 | sylib 188 | 
. . . . . . . . . . 11
       
1c 
  Nc                 ∼   
             | 
| 19 | 14, 18 | anim12i 549 | 
. . . . . . . . . 10
        
1c 
  Nc          1c   
Nc         
      
  ∼                             
∼                  | 
| 20 |   | reeanv 2779 | 
. . . . . . . . . . . . 13
       
∼       ∼                                         
∼                      
∼                  | 
| 21 | 20 | 2rexbii 2642 | 
. . . . . . . . . . . 12
       
              ∼       ∼    
                                                   ∼               
       ∼                  | 
| 22 |   | reeanv 2779 | 
. . . . . . . . . . . 12
       
               ∼               
       ∼                        
       ∼               
              ∼   
              | 
| 23 | 21, 22 | bitri 240 | 
. . . . . . . . . . 11
       
              ∼       ∼    
                                    
       ∼               
              ∼   
              | 
| 24 |   | ncseqnc 6129 | 
. . . . . . . . . . . . . . 15
       NC        Nc             | 
| 25 |   | ncseqnc 6129 | 
. . . . . . . . . . . . . . 15
       NC        Nc             | 
| 26 | 24, 25 | bi2anan9 843 | 
. . . . . . . . . . . . . 14
        NC       NC           Nc         Nc                
       | 
| 27 | 26 | biimpar 471 | 
. . . . . . . . . . . . 13
         NC       NC                          
  Nc         Nc     | 
| 28 |   | eqtr2 2371 | 
. . . . . . . . . . . . . . . 16
                                                
           | 
| 29 |   | vex 2863 | 
. . . . . . . . . . . . . . . . . 18
        | 
| 30 | 29 | elcompl 3226 | 
. . . . . . . . . . . . . . . . 17
       ∼              | 
| 31 |   | vex 2863 | 
. . . . . . . . . . . . . . . . . 18
        | 
| 32 | 31 | elcompl 3226 | 
. . . . . . . . . . . . . . . . 17
       ∼              | 
| 33 |   | vex 2863 | 
. . . . . . . . . . . . . . . . . . . . 21
        | 
| 34 |   | vex 2863 | 
. . . . . . . . . . . . . . . . . . . . 21
        | 
| 35 | 33, 34, 29, 31 | enadj 6061 | 
. . . . . . . . . . . . . . . . . . . 20
                         
         
                    | 
| 36 | 35 | 3expb 1152 | 
. . . . . . . . . . . . . . . . . . 19
                         
      
                         | 
| 37 | 36 | ancoms 439 | 
. . . . . . . . . . . . . . . . . 18
                                     
                    | 
| 38 | 37 | ex 423 | 
. . . . . . . . . . . . . . . . 17
                                   
                      | 
| 39 | 30, 32, 38 | syl2anb 465 | 
. . . . . . . . . . . . . . . 16
        ∼
       
∼                                       | 
| 40 | 28, 39 | syl5 28 | 
. . . . . . . . . . . . . . 15
        ∼
       
∼                                                 | 
| 41 | 40 | rexlimivv 2744 | 
. . . . . . . . . . . . . 14
       
∼       ∼                                           | 
| 42 |   | eqeq12 2365 | 
. . . . . . . . . . . . . . 15
        Nc         Nc               Nc     Nc     | 
| 43 | 33 | eqnc 6128 | 
. . . . . . . . . . . . . . 15
    Nc     Nc            | 
| 44 | 42, 43 | syl6bb 252 | 
. . . . . . . . . . . . . 14
        Nc         Nc                       | 
| 45 | 41, 44 | syl5ibr 212 | 
. . . . . . . . . . . . 13
        Nc         Nc            ∼       ∼    
                                       | 
| 46 | 27, 45 | syl 15 | 
. . . . . . . . . . . 12
         NC       NC                              ∼    
  ∼                                            | 
| 47 | 46 | rexlimdvva 2746 | 
. . . . . . . . . . 11
        NC       NC          
              ∼       ∼    
                                       | 
| 48 | 23, 47 | syl5bir 209 | 
. . . . . . . . . 10
        NC       NC         
      
  ∼                             
∼                      
    | 
| 49 | 19, 48 | syl5 28 | 
. . . . . . . . 9
        NC       NC           
1c 
  Nc          1c   
Nc              | 
| 50 | 49 | imp 418 | 
. . . . . . . 8
         NC       NC          
1c 
  Nc          1c   
Nc          
   | 
| 51 | 7, 50 | sylan2 460 | 
. . . . . . 7
         NC       NC          
1c 
       1c         1c   
Nc          
   | 
| 52 | 51 | expr 598 | 
. . . . . 6
         NC       NC          1c   
     1c  
     
 
1c 
  Nc             | 
| 53 | 52 | exlimdv 1636 | 
. . . . 5
         NC       NC          1c   
     1c  
          1c    Nc             | 
| 54 | 4, 53 | syl5bi 208 | 
. . . 4
         NC       NC          1c   
     1c  
     
 
1c 
  NC           | 
| 55 | 3, 54 | mpd 14 | 
. . 3
         NC       NC          1c   
     1c  
         | 
| 56 | 55 | ex 423 | 
. 2
        NC       NC          
1c 
       1c            | 
| 57 |   | addceq1 4384 | 
. 2
                1c         1c   | 
| 58 | 56, 57 | impbid1 194 | 
1
        NC       NC          
1c 
       1c            |