| Step | Hyp | Ref
| Expression |
| 1 | | vex 2863 |
. . . . . . 7
 |
| 2 | 1 | elimak 4260 |
. . . . . 6
  Sk  1 k    k1c  1c   
Sk  1 k     |
| 3 | | el1c 4140 |
. . . . . . . . . 10
 1c 
    |
| 4 | 3 | anbi1i 676 |
. . . . . . . . 9
 
1c    Sk  1 k     
    
Sk  1 k      |
| 5 | | 19.41v 1901 |
. . . . . . . . 9
        
Sk  1 k     
    
Sk  1 k      |
| 6 | 4, 5 | bitr4i 243 |
. . . . . . . 8
 
1c    Sk  1 k      
    
Sk  1 k      |
| 7 | 6 | exbii 1582 |
. . . . . . 7
    1c    Sk  1 k              Sk  1 k      |
| 8 | | df-rex 2621 |
. . . . . . 7
 
1c    Sk  1 k     
1c
  
Sk  1 k      |
| 9 | | excom 1741 |
. . . . . . 7
           Sk  1 k              Sk  1 k      |
| 10 | 7, 8, 9 | 3bitr4i 268 |
. . . . . 6
 
1c    Sk  1 k             Sk  1 k      |
| 11 | 2, 10 | bitri 240 |
. . . . 5
  Sk  1 k    k1c     
    
Sk  1 k      |
| 12 | | snex 4112 |
. . . . . . . 8
 
 |
| 13 | | opkeq1 4060 |
. . . . . . . . 9
             |
| 14 | 13 | eleq1d 2419 |
. . . . . . . 8
       Sk  1 k      
 Sk  1 k      |
| 15 | 12, 14 | ceqsexv 2895 |
. . . . . . 7
        
Sk  1 k       
 Sk  1 k     |
| 16 | | eldif 3222 |
. . . . . . . 8
      Sk  1 k         Sk       1 k     |
| 17 | | vex 2863 |
. . . . . . . . . 10
 |
| 18 | 17, 1 | elssetk 4271 |
. . . . . . . . 9
      Sk   |
| 19 | 12, 1 | opkelxpk 4249 |
. . . . . . . . . . . 12
       1 k     1    |
| 20 | 1, 19 | mpbiran2 885 |
. . . . . . . . . . 11
       1 k    1   |
| 21 | | snelpw1 4147 |
. . . . . . . . . . 11
   1   |
| 22 | 20, 21 | bitri 240 |
. . . . . . . . . 10
       1 k    |
| 23 | 22 | notbii 287 |
. . . . . . . . 9
       1 k 
  |
| 24 | 18, 23 | anbi12i 678 |
. . . . . . . 8
       Sk     
 1 k   
   |
| 25 | | annim 414 |
. . . . . . . 8
 
     |
| 26 | 16, 24, 25 | 3bitri 262 |
. . . . . . 7
      Sk  1 k   
   |
| 27 | 15, 26 | bitri 240 |
. . . . . 6
        
Sk  1 k    
   |
| 28 | 27 | exbii 1582 |
. . . . 5
           Sk  1 k         |
| 29 | | exnal 1574 |
. . . . 5
          |
| 30 | 11, 28, 29 | 3bitri 262 |
. . . 4
  Sk  1 k    k1c   
   |
| 31 | 30 | con2bii 322 |
. . 3
      Sk  1 k    k1c  |
| 32 | 1 | elpw 3729 |
. . . 4
    |
| 33 | | dfss2 3263 |
. . . 4
   
   |
| 34 | 32, 33 | bitri 240 |
. . 3
    
   |
| 35 | 1 | elcompl 3226 |
. . 3
 ∼  Sk  1 k    k1c  Sk  1 k    k1c  |
| 36 | 31, 34, 35 | 3bitr4i 268 |
. 2
  ∼ 
Sk  1 k    k1c  |
| 37 | 36 | eqriv 2350 |
1
 ∼  Sk  1 k    k1c |