| Step | Hyp | Ref
| Expression |
| 1 | | nns.s |
. 2

ℕ∞               |
| 2 | | 1lt2o 6509 |
. . . . . . 7
 |
| 3 | 2 | a1i 9 |
. . . . . 6
 
ℕ∞    |
| 4 | | nninff 7197 |
. . . . . . . 8
 ℕ∞       |
| 5 | 4 | adantr 276 |
. . . . . . 7
 
ℕ∞        |
| 6 | | nnpredcl 4660 |
. . . . . . . 8
    |
| 7 | 6 | adantl 277 |
. . . . . . 7
 
ℕ∞     |
| 8 | 5, 7 | ffvelcdmd 5701 |
. . . . . 6
 
ℕ∞         |
| 9 | | nndceq0 4655 |
. . . . . . 7

DECID
  |
| 10 | 9 | adantl 277 |
. . . . . 6
 
ℕ∞  DECID   |
| 11 | 3, 8, 10 | ifcldcd 3598 |
. . . . 5
 
ℕ∞              |
| 12 | | eqid 2196 |
. . . . 5
                         |
| 13 | 11, 12 | fmptd 5719 |
. . . 4
 ℕ∞                   |
| 14 | | 2onn 6588 |
. . . . 5
 |
| 15 | | omex 4630 |
. . . . 5
 |
| 16 | | elmapg 6729 |
. . . . 5
                                     |
| 17 | 14, 15, 16 | mp2an 426 |
. . . 4
                                 |
| 18 | 13, 17 | sylibr 134 |
. . 3
 ℕ∞                 |
| 19 | | 1on 6490 |
. . . . . . . . 9
 |
| 20 | 19 | ontrci 4463 |
. . . . . . . 8
 |
| 21 | 2 | a1i 9 |
. . . . . . . . . . 11
 
ℕ∞    |
| 22 | 4 | adantr 276 |
. . . . . . . . . . . 12
 
ℕ∞        |
| 23 | | peano2 4632 |
. . . . . . . . . . . . . 14

  |
| 24 | 23 | adantl 277 |
. . . . . . . . . . . . 13
 
ℕ∞ 
  |
| 25 | | nnpredcl 4660 |
. . . . . . . . . . . . 13
    |
| 26 | 24, 25 | syl 14 |
. . . . . . . . . . . 12
 
ℕ∞     |
| 27 | 22, 26 | ffvelcdmd 5701 |
. . . . . . . . . . 11
 
ℕ∞         |
| 28 | | nndceq0 4655 |
. . . . . . . . . . . 12
 DECID   |
| 29 | 24, 28 | syl 14 |
. . . . . . . . . . 11
 
ℕ∞  DECID
  |
| 30 | 21, 27, 29 | ifcldcd 3598 |
. . . . . . . . . 10
 
ℕ∞              |
| 31 | 30 | adantr 276 |
. . . . . . . . 9
  
ℕ∞               |
| 32 | | df-2o 6484 |
. . . . . . . . 9
 |
| 33 | 31, 32 | eleqtrdi 2289 |
. . . . . . . 8
  
ℕ∞               |
| 34 | | trsucss 4459 |
. . . . . . . 8

                        |
| 35 | 20, 33, 34 | mpsyl 65 |
. . . . . . 7
  
ℕ∞               |
| 36 | | iftrue 3567 |
. . . . . . . 8

            |
| 37 | 36 | adantl 277 |
. . . . . . 7
  
ℕ∞               |
| 38 | 35, 37 | sseqtrrd 3223 |
. . . . . 6
  
ℕ∞                         |
| 39 | | simpr 110 |
. . . . . . . . . . . 12
 
ℕ∞    |
| 40 | 39 | adantr 276 |
. . . . . . . . . . 11
  
ℕ∞  
  |
| 41 | | nnord 4649 |
. . . . . . . . . . 11
   |
| 42 | | ordtr 4414 |
. . . . . . . . . . 11

  |
| 43 | 40, 41, 42 | 3syl 17 |
. . . . . . . . . 10
  
ℕ∞  
  |
| 44 | | unisucg 4450 |
. . . . . . . . . . 11
 
    |
| 45 | 40, 44 | syl 14 |
. . . . . . . . . 10
  
ℕ∞  
     |
| 46 | 43, 45 | mpbid 147 |
. . . . . . . . 9
  
ℕ∞  

  |
| 47 | 46 | fveq2d 5565 |
. . . . . . . 8
  
ℕ∞  
           |
| 48 | | simpr 110 |
. . . . . . . . . . . 12
  
ℕ∞  
  |
| 49 | 48 | neqned 2374 |
. . . . . . . . . . 11
  
ℕ∞  
  |
| 50 | | nnsucpred 4654 |
. . . . . . . . . . 11
      |
| 51 | 40, 49, 50 | syl2anc 411 |
. . . . . . . . . 10
  
ℕ∞  

  |
| 52 | 51 | fveq2d 5565 |
. . . . . . . . 9
  
ℕ∞  
  
        |
| 53 | | suceq 4438 |
. . . . . . . . . . . 12
 
   |
| 54 | 53 | fveq2d 5565 |
. . . . . . . . . . 11
             |
| 55 | | fveq2 5561 |
. . . . . . . . . . 11
             |
| 56 | 54, 55 | sseq12d 3215 |
. . . . . . . . . 10
                        |
| 57 | | fveq1 5560 |
. . . . . . . . . . . . . . . 16
           |
| 58 | | fveq1 5560 |
. . . . . . . . . . . . . . . 16
           |
| 59 | 57, 58 | sseq12d 3215 |
. . . . . . . . . . . . . . 15
             
       |
| 60 | 59 | ralbidv 2497 |
. . . . . . . . . . . . . 14
  
                    |
| 61 | | df-nninf 7195 |
. . . . . . . . . . . . . 14
ℕ∞   
           |
| 62 | 60, 61 | elrab2 2923 |
. . . . . . . . . . . . 13
 ℕ∞    
           |
| 63 | 62 | simprbi 275 |
. . . . . . . . . . . 12
 ℕ∞            |
| 64 | | suceq 4438 |
. . . . . . . . . . . . . . 15

  |
| 65 | 64 | fveq2d 5565 |
. . . . . . . . . . . . . 14
           |
| 66 | | fveq2 5561 |
. . . . . . . . . . . . . 14
           |
| 67 | 65, 66 | sseq12d 3215 |
. . . . . . . . . . . . 13
             
       |
| 68 | 67 | cbvralv 2729 |
. . . . . . . . . . . 12
 
       
           |
| 69 | 63, 68 | sylib 122 |
. . . . . . . . . . 11
 ℕ∞            |
| 70 | 69 | ad2antrr 488 |
. . . . . . . . . 10
  
ℕ∞  
           |
| 71 | | nnpredcl 4660 |
. . . . . . . . . . . 12
    |
| 72 | 71 | adantl 277 |
. . . . . . . . . . 11
 
ℕ∞     |
| 73 | 72 | adantr 276 |
. . . . . . . . . 10
  
ℕ∞  
   |
| 74 | 56, 70, 73 | rspcdva 2873 |
. . . . . . . . 9
  
ℕ∞  
  
 
       |
| 75 | 52, 74 | eqsstrrd 3221 |
. . . . . . . 8
  
ℕ∞  
           |
| 76 | 47, 75 | eqsstrd 3220 |
. . . . . . 7
  
ℕ∞  
    
       |
| 77 | | peano3 4633 |
. . . . . . . . . 10
   |
| 78 | 77 | neneqd 2388 |
. . . . . . . . 9

  |
| 79 | 78 | ad2antlr 489 |
. . . . . . . 8
  
ℕ∞  
  |
| 80 | 79 | iffalsed 3572 |
. . . . . . 7
  
ℕ∞  
                 |
| 81 | 48 | iffalsed 3572 |
. . . . . . 7
  
ℕ∞  
                 |
| 82 | 76, 80, 81 | 3sstr4d 3229 |
. . . . . 6
  
ℕ∞  
                      |
| 83 | | nndceq0 4655 |
. . . . . . . 8

DECID
  |
| 84 | 83 | adantl 277 |
. . . . . . 7
 
ℕ∞  DECID   |
| 85 | | exmiddc 837 |
. . . . . . 7
DECID     |
| 86 | 84, 85 | syl 14 |
. . . . . 6
 
ℕ∞      |
| 87 | 38, 82, 86 | mpjaodan 799 |
. . . . 5
 
ℕ∞                        |
| 88 | | eqeq1 2203 |
. . . . . . . 8
 
   |
| 89 | | unieq 3849 |
. . . . . . . . 9
 
   |
| 90 | 89 | fveq2d 5565 |
. . . . . . . 8
             |
| 91 | 88, 90 | ifbieq2d 3586 |
. . . . . . 7
                       |
| 92 | 91, 12 | fvmptg 5640 |
. . . . . 6
                                         |
| 93 | 24, 30, 92 | syl2anc 411 |
. . . . 5
 
ℕ∞                
             |
| 94 | 22, 72 | ffvelcdmd 5701 |
. . . . . . 7
 
ℕ∞         |
| 95 | 21, 94, 84 | ifcldcd 3598 |
. . . . . 6
 
ℕ∞              |
| 96 | | eqeq1 2203 |
. . . . . . . 8
 
   |
| 97 | | unieq 3849 |
. . . . . . . . 9
     |
| 98 | 97 | fveq2d 5565 |
. . . . . . . 8
             |
| 99 | 96, 98 | ifbieq2d 3586 |
. . . . . . 7
                       |
| 100 | 99, 12 | fvmptg 5640 |
. . . . . 6
                                         |
| 101 | 39, 95, 100 | syl2anc 411 |
. . . . 5
 
ℕ∞                              |
| 102 | 87, 93, 101 | 3sstr4d 3229 |
. . . 4
 
ℕ∞                
                   |
| 103 | 102 | ralrimiva 2570 |
. . 3
 ℕ∞                
                   |
| 104 | | fveq1 5560 |
. . . . . 6
                                   |
| 105 | | fveq1 5560 |
. . . . . 6
                                   |
| 106 | 104, 105 | sseq12d 3215 |
. . . . 5
                
                   
                    |
| 107 | 106 | ralbidv 2497 |
. . . 4
                                                           |
| 108 | 107, 61 | elrab2 2923 |
. . 3
            
ℕ∞                               
                    |
| 109 | 18, 103, 108 | sylanbrc 417 |
. 2
 ℕ∞            
ℕ∞ |
| 110 | 1, 109 | fmpti 5717 |
1
 ℕ∞ ℕ∞ |