| 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         |