| Step | Hyp | Ref
| Expression |
| 1 | | nchoicelem10.2 |
. 2
 |
| 2 | | elrn 4897 |
. . . . 5
       ∼ S  S  S Image      ∼
S  S  S Image       
   |
| 3 | | trtxp 5782 |
. . . . . . 7
   ∼
S  S  S Image       
   ∼
S     S  S Image      |
| 4 | | brcnv 4893 |
. . . . . . . . . 10
  ∼ S     ∼ S   |
| 5 | | df-br 4641 |
. . . . . . . . . 10
   ∼ S      ∼
S  |
| 6 | | snex 4112 |
. . . . . . . . . . . . 13
 
 |
| 7 | | vex 2863 |
. . . . . . . . . . . . 13
 |
| 8 | 6, 7 | opex 4589 |
. . . . . . . . . . . 12
   
  |
| 9 | 8 | elcompl 3226 |
. . . . . . . . . . 11
      ∼ S      S  |
| 10 | | vex 2863 |
. . . . . . . . . . . 12
 |
| 11 | 10, 7 | opelssetsn 4761 |
. . . . . . . . . . 11
      S   |
| 12 | 9, 11 | xchbinx 301 |
. . . . . . . . . 10
      ∼ S   |
| 13 | 4, 5, 12 | 3bitri 262 |
. . . . . . . . 9
  ∼ S     |
| 14 | | brres 4950 |
. . . . . . . . . 10
   S  S Image     S
 S Image    |
| 15 | | brcnv 4893 |
. . . . . . . . . . . 12
  S S   |
| 16 | 1, 7 | brsset 4759 |
. . . . . . . . . . . 12
 S   |
| 17 | 15, 16 | bitri 240 |
. . . . . . . . . . 11
  S
  |
| 18 | | elfix 5788 |
. . . . . . . . . . . 12
  S
Image  S Image    |
| 19 | | brco 4884 |
. . . . . . . . . . . . 13
  S Image     Image S    |
| 20 | | vex 2863 |
. . . . . . . . . . . . . . . 16
 |
| 21 | 7, 20 | brimage 5794 |
. . . . . . . . . . . . . . 15
 Image
      |
| 22 | 20, 7 | brsset 4759 |
. . . . . . . . . . . . . . 15
 S   |
| 23 | 21, 22 | anbi12i 678 |
. . . . . . . . . . . . . 14
  Image S          |
| 24 | 23 | exbii 1582 |
. . . . . . . . . . . . 13
    Image S 
  
       |
| 25 | | nchoicelem10.1 |
. . . . . . . . . . . . . . 15
 |
| 26 | 25, 7 | imaex 4748 |
. . . . . . . . . . . . . 14
     |
| 27 | | sseq1 3293 |
. . . . . . . . . . . . . 14
    
        |
| 28 | 26, 27 | ceqsexv 2895 |
. . . . . . . . . . . . 13
       
       |
| 29 | 19, 24, 28 | 3bitri 262 |
. . . . . . . . . . . 12
  S Image        |
| 30 | 18, 29 | bitri 240 |
. . . . . . . . . . 11
  S
Image       |
| 31 | 17, 30 | anbi12i 678 |
. . . . . . . . . 10
   S  S Image  
       |
| 32 | 14, 31 | bitri 240 |
. . . . . . . . 9
   S  S Image       
   |
| 33 | 13, 32 | anbi12i 678 |
. . . . . . . 8
   ∼
S     S  S Image     
        |
| 34 | | ancom 437 |
. . . . . . . 8
              
    |
| 35 | 33, 34 | bitri 240 |
. . . . . . 7
   ∼
S     S  S Image         
    |
| 36 | | annim 414 |
. . . . . . 7
       
  
    
   |
| 37 | 3, 35, 36 | 3bitri 262 |
. . . . . 6
   ∼
S  S  S Image       
      
    |
| 38 | 37 | exbii 1582 |
. . . . 5
    ∼ S  S
 S Image       
   
        |
| 39 | | exnal 1574 |
. . . . 5
   
    
        
    |
| 40 | 2, 38, 39 | 3bitrri 263 |
. . . 4
    
    
    
  ∼ S  S
 S Image     |
| 41 | 40 | con1bii 321 |
. . 3
       ∼ S  S  S Image           
   |
| 42 | 6, 1 | opex 4589 |
. . . 4
   
  |
| 43 | 42 | elcompl 3226 |
. . 3
      ∼
 ∼ S
 S  S Image         ∼ S  S  S Image     |
| 44 | | df-clos1 5874 |
. . . . 5
Clos1   
          |
| 45 | 44 | eleq2i 2417 |
. . . 4
 Clos1     
         |
| 46 | 10 | elintab 3938 |
. . . 4
             
    
   |
| 47 | 45, 46 | bitri 240 |
. . 3
 Clos1       
    
   |
| 48 | 41, 43, 47 | 3bitr4i 268 |
. 2
      ∼
 ∼ S
 S  S Image   Clos1      |
| 49 | 1, 48 | releqel 5808 |
1
  
 ∼  Ins3 S Ins2 ∼  ∼
S  S  S Image     1c
Clos1      |