| Step | Hyp | Ref
| Expression |
| 1 | | frecrdg.1 |
. . . 4
   |
| 2 | | vex 2766 |
. . . . . 6
 |
| 3 | | funfvex 5578 |
. . . . . . 7
         |
| 4 | 3 | funfni 5361 |
. . . . . 6
 
       |
| 5 | 2, 4 | mpan2 425 |
. . . . 5
       |
| 6 | 5 | alrimiv 1888 |
. . . 4
         |
| 7 | 1, 6 | syl 14 |
. . 3
         |
| 8 | | frecrdg.2 |
. . 3
   |
| 9 | | frecfnom 6468 |
. . 3
       
 frec     |
| 10 | 7, 8, 9 | syl2anc 411 |
. 2
 frec     |
| 11 | | rdgifnon2 6447 |
. . . 4
       
       |
| 12 | 7, 8, 11 | syl2anc 411 |
. . 3
       |
| 13 | | omsson 4650 |
. . 3
 |
| 14 | | fnssres 5374 |
. . 3
            
  |
| 15 | 12, 13, 14 | sylancl 413 |
. 2
      
  |
| 16 | | fveq2 5561 |
. . . . 5

frec      frec        |
| 17 | | fveq2 5561 |
. . . . 5

                      |
| 18 | 16, 17 | eqeq12d 2211 |
. . . 4

 frec               
frec 
                 |
| 19 | | fveq2 5561 |
. . . . 5
 frec      frec        |
| 20 | | fveq2 5561 |
. . . . 5
                       |
| 21 | 19, 20 | eqeq12d 2211 |
. . . 4
  frec               
frec 
                 |
| 22 | | fveq2 5561 |
. . . . 5
 frec      frec    
   |
| 23 | | fveq2 5561 |
. . . . 5
     
                 |
| 24 | 22, 23 | eqeq12d 2211 |
. . . 4
  frec                frec                   |
| 25 | | frec0g 6464 |
. . . . . 6
 frec        |
| 26 | 8, 25 | syl 14 |
. . . . 5
 frec        |
| 27 | | peano1 4631 |
. . . . . . 7
 |
| 28 | | fvres 5585 |
. . . . . . 7

                    |
| 29 | 27, 28 | ax-mp 5 |
. . . . . 6
                   |
| 30 | | rdg0g 6455 |
. . . . . . 7
           |
| 31 | 8, 30 | syl 14 |
. . . . . 6
           |
| 32 | 29, 31 | eqtrid 2241 |
. . . . 5
     
       |
| 33 | 26, 32 | eqtr4d 2232 |
. . . 4
 frec          
       |
| 34 | | simpr 110 |
. . . . . . . . . 10
    frec          
      frec          
       |
| 35 | | fvres 5585 |
. . . . . . . . . . 11
              
      |
| 36 | 35 | ad2antlr 489 |
. . . . . . . . . 10
    frec          
                   
      |
| 37 | 34, 36 | eqtrd 2229 |
. . . . . . . . 9
    frec          
      frec                |
| 38 | 37 | fveq2d 5565 |
. . . . . . . 8
    frec          
         frec 
                   |
| 39 | 7, 8 | jca 306 |
. . . . . . . . . 10
           |
| 40 | | simp1 999 |
. . . . . . . . . . . . 13
       
         |
| 41 | | ralv 2780 |
. . . . . . . . . . . . 13
 
            |
| 42 | 40, 41 | sylibr 134 |
. . . . . . . . . . . 12
       
        |
| 43 | | simp2 1000 |
. . . . . . . . . . . . 13
       
   |
| 44 | 43 | elexd 2776 |
. . . . . . . . . . . 12
       
   |
| 45 | | simp3 1001 |
. . . . . . . . . . . 12
       
   |
| 46 | | frecsuc 6474 |
. . . . . . . . . . . 12
        frec    
    frec         |
| 47 | 42, 44, 45, 46 | syl3anc 1249 |
. . . . . . . . . . 11
       
 frec         frec         |
| 48 | 47 | 3expa 1205 |
. . . . . . . . . 10
           frec    
    frec         |
| 49 | 39, 48 | sylan 283 |
. . . . . . . . 9
 

frec 
       frec         |
| 50 | 49 | adantr 276 |
. . . . . . . 8
    frec          
      frec    
    frec         |
| 51 | 1 | adantr 276 |
. . . . . . . . . 10
 

  |
| 52 | 8 | adantr 276 |
. . . . . . . . . 10
 

  |
| 53 | | simpr 110 |
. . . . . . . . . . 11
 

  |
| 54 | | nnon 4647 |
. . . . . . . . . . 11
   |
| 55 | 53, 54 | syl 14 |
. . . . . . . . . 10
 

  |
| 56 | | frecrdg.inc |
. . . . . . . . . . 11
        |
| 57 | 56 | adantr 276 |
. . . . . . . . . 10
 

       |
| 58 | 51, 52, 55, 57 | rdgisucinc 6452 |
. . . . . . . . 9
 

      
               |
| 59 | 58 | adantr 276 |
. . . . . . . 8
    frec          
                            |
| 60 | 38, 50, 59 | 3eqtr4d 2239 |
. . . . . . 7
    frec          
      frec    
    
      |
| 61 | | peano2 4632 |
. . . . . . . . 9

  |
| 62 | | fvres 5585 |
. . . . . . . . 9
                     |
| 63 | 61, 62 | syl 14 |
. . . . . . . 8
                     |
| 64 | 63 | ad2antlr 489 |
. . . . . . 7
    frec          
                          |
| 65 | 60, 64 | eqtr4d 2232 |
. . . . . 6
    frec          
      frec    
             |
| 66 | 65 | ex 115 |
. . . . 5
 

 frec          
    
frec 
        
        |
| 67 | 66 | expcom 116 |
. . . 4
   frec          
    
frec 
        
         |
| 68 | 18, 21, 24, 33, 67 | finds2 4638 |
. . 3
  frec                   |
| 69 | 68 | impcom 125 |
. 2
 

frec 
                |
| 70 | 10, 15, 69 | eqfnfvd 5665 |
1
 frec           |