| Step | Hyp | Ref
| Expression |
| 1 | | ss2iundf.xph |
. . 3
   |
| 2 | | ss2iundf.ss |
. . . . 5
 
   |
| 3 | | df-ral 2917 |
. . . . . . . 8
 
      |
| 4 | | ss2iundf.el |
. . . . . . . . 9
 
   |
| 5 | | ss2iundf.yph |
. . . . . . . . . . . 12
   |
| 6 | | ss2iundf.a |
. . . . . . . . . . . . 13
   |
| 7 | 6 | nfcri 2758 |
. . . . . . . . . . . 12
  |
| 8 | 5, 7 | nfan 1828 |
. . . . . . . . . . 11
     |
| 9 | | simpr 477 |
. . . . . . . . . . . . . . 15
       |
| 10 | 9 | eleq1d 2686 |
. . . . . . . . . . . . . 14
     
   |
| 11 | 10 | biimprd 238 |
. . . . . . . . . . . . 13
     
   |
| 12 | | ss2iundf.sub |
. . . . . . . . . . . . . . . . 17
 

  |
| 13 | 12 | sseq2d 3633 |
. . . . . . . . . . . . . . . 16
 


   |
| 14 | 13 | 3expa 1265 |
. . . . . . . . . . . . . . 15
     
   |
| 15 | 14 | notbid 308 |
. . . . . . . . . . . . . 14
     
   |
| 16 | 15 | biimpd 219 |
. . . . . . . . . . . . 13
     
   |
| 17 | 11, 16 | imim12d 81 |
. . . . . . . . . . . 12
       

    |
| 18 | 17 | ex 450 |
. . . . . . . . . . 11
 
   
 
     |
| 19 | 8, 18 | alrimi 2082 |
. . . . . . . . . 10
 
             |
| 20 | | ss2iundf.y |
. . . . . . . . . . . . 13
   |
| 21 | | ss2iundf.yc |
. . . . . . . . . . . . 13
   |
| 22 | 20, 21 | nfel 2777 |
. . . . . . . . . . . 12
  |
| 23 | | ss2iundf.b |
. . . . . . . . . . . . . 14
   |
| 24 | | ss2iundf.g |
. . . . . . . . . . . . . 14
   |
| 25 | 23, 24 | nfss 3596 |
. . . . . . . . . . . . 13

 |
| 26 | 25 | nfn 1784 |
. . . . . . . . . . . 12
  |
| 27 | 22, 26 | nfim 1825 |
. . . . . . . . . . 11
     |
| 28 | 27, 20 | spcimgft 3284 |
. . . . . . . . . 10
   
 
 
   
   
 
     |
| 29 | 19, 4, 28 | sylc 65 |
. . . . . . . . 9
 
    
 
    |
| 30 | 4, 29 | mpid 44 |
. . . . . . . 8
 
    
    |
| 31 | 3, 30 | syl5bi 232 |
. . . . . . 7
 
  
   |
| 32 | 31 | con2d 129 |
. . . . . 6
 
      |
| 33 | | dfrex2 2996 |
. . . . . 6
 

  |
| 34 | 32, 33 | syl6ibr 242 |
. . . . 5
 
  
   |
| 35 | 2, 34 | mpd 15 |
. . . 4
 
 
  |
| 36 | 35 | ex 450 |
. . 3
      |
| 37 | 1, 36 | ralrimi 2957 |
. 2
  
  |
| 38 | | ssel 3597 |
. . . . . . . 8
     |
| 39 | 38 | reximi 3011 |
. . . . . . 7
 


   |
| 40 | 23 | nfcri 2758 |
. . . . . . . 8
  |
| 41 | 40 | r19.37 3086 |
. . . . . . 7
    

   |
| 42 | 39, 41 | syl 17 |
. . . . . 6
 


   |
| 43 | | eliun 4524 |
. . . . . 6
 

  |
| 44 | 42, 43 | syl6ibr 242 |
. . . . 5
 

    |
| 45 | 44 | ssrdv 3609 |
. . . 4
 

  |
| 46 | 45 | ralimi 2952 |
. . 3
 



  |
| 47 | | df-iun 4522 |
. . . . 5

 
  |
| 48 | 47 | sseq1i 3629 |
. . . 4
 
  
 
  |
| 49 | | abss 3671 |
. . . 4
  


    
   |
| 50 | | dfss2 3591 |
. . . . . 6
         |
| 51 | 50 | ralbii 2980 |
. . . . 5
 
    
    |
| 52 | | ralcom4 3224 |
. . . . 5
 
  
    

    |
| 53 | | ss2iundf.xc |
. . . . . . . . 9
   |
| 54 | | ss2iundf.d |
. . . . . . . . 9
   |
| 55 | 53, 54 | nfiun 4548 |
. . . . . . . 8
  
 |
| 56 | 55 | nfcri 2758 |
. . . . . . 7

  |
| 57 | 56 | r19.23 3022 |
. . . . . 6
 
 
  
    |
| 58 | 57 | albii 1747 |
. . . . 5
     
    

   |
| 59 | 51, 52, 58 | 3bitrri 287 |
. . . 4
    

     |
| 60 | 48, 49, 59 | 3bitri 286 |
. . 3
 
     |
| 61 | 46, 60 | sylibr 224 |
. 2
 

 
  |
| 62 | 37, 61 | syl 17 |
1
     |