| Step | Hyp | Ref
| Expression |
| 1 | | issubc.c |
. 2
   |
| 2 | | issubc.s |
. 2
   |
| 3 | | simpl 473 |
. . . . 5
 

  |
| 4 | | sscpwex 16475 |
. . . . . . . 8
 cat  f     |
| 5 | | simpl 473 |
. . . . . . . . 9
  cat 
f     ![]. ].](_drbrack.gif)                                    comp            cat  f     |
| 6 | 5 | ss2abi 3674 |
. . . . . . . 8
  cat  f     ![]. ].](_drbrack.gif) 
                                  comp            

cat
 f     |
| 7 | 4, 6 | ssexi 4803 |
. . . . . . 7
  cat  f     ![]. ].](_drbrack.gif) 
                                  comp              |
| 8 | 7 | csbex 4793 |
. . . . . 6
  ![]_ ]_](_urbrack.gif)   cat 
f     ![]. ].](_drbrack.gif)                                    comp              |
| 9 | 8 | a1i 11 |
. . . . 5
 

  ![]_ ]_](_urbrack.gif)   cat  f     ![]. ].](_drbrack.gif) 
                                  comp               |
| 10 | | df-subc 16472 |
. . . . . 6
Subcat    cat 
f     ![]. ].](_drbrack.gif)                                    comp               |
| 11 | 10 | fvmpts 6285 |
. . . . 5
    ![]_ ]_](_urbrack.gif)   cat 
f     ![]. ].](_drbrack.gif)                                    comp              Subcat    ![]_ ]_](_urbrack.gif)   cat 
f     ![]. ].](_drbrack.gif)                                    comp               |
| 12 | 3, 9, 11 | syl2anc 693 |
. . . 4
 

Subcat    ![]_ ]_](_urbrack.gif)   cat 
f     ![]. ].](_drbrack.gif)                                    comp               |
| 13 | 12 | eleq2d 2687 |
. . 3
 

 Subcat    ![]_ ]_](_urbrack.gif)   cat  f     ![]. ].](_drbrack.gif) 
                                  comp                |
| 14 | | sbcel2 3989 |
. . . 4
   ![]. ].](_drbrack.gif)   cat 
f     ![]. ].](_drbrack.gif)                                    comp            
  ![]_ ]_](_urbrack.gif)   cat 
f     ![]. ].](_drbrack.gif)                                    comp               |
| 15 | 14 | a1i 11 |
. . 3
 

   ![]. ].](_drbrack.gif)   cat 
f     ![]. ].](_drbrack.gif)                                    comp            
  ![]_ ]_](_urbrack.gif)   cat 
f     ![]. ].](_drbrack.gif)                                    comp                |
| 16 | | elex 3212 |
. . . . . 6
   cat  f     ![]. ].](_drbrack.gif) 
                                  comp            
  |
| 17 | 16 | a1i 11 |
. . . . 5
     
  cat  f     ![]. ].](_drbrack.gif) 
                                  comp            
   |
| 18 | | sscrel 16473 |
. . . . . . . 8
cat |
| 19 | 18 | brrelexi 5158 |
. . . . . . 7
 cat
  |
| 20 | 19 | adantr 481 |
. . . . . 6
  cat 
       

                             |
| 21 | 20 | a1i 11 |
. . . . 5
       cat          

     
                   
   |
| 22 | | df-sbc 3436 |
. . . . . . 7
   ![]. ].](_drbrack.gif)  cat 
f     ![]. ].](_drbrack.gif)                                    comp              cat  f     ![]. ].](_drbrack.gif) 
                                  comp               |
| 23 | | simpr 477 |
. . . . . . . 8
   


   |
| 24 | | simpr 477 |
. . . . . . . . . . 11
   



  |
| 25 | | simpr 477 |
. . . . . . . . . . . . . 14
       |
| 26 | 25 | fveq2d 6195 |
. . . . . . . . . . . . 13
      f    f     |
| 27 | | issubc.h |
. . . . . . . . . . . . 13

f    |
| 28 | 26, 27 | syl6eqr 2674 |
. . . . . . . . . . . 12
      f     |
| 29 | 28 | adantr 481 |
. . . . . . . . . . 11
   



 f     |
| 30 | 24, 29 | breq12d 4666 |
. . . . . . . . . 10
   



 cat  f  
cat    |
| 31 | | vex 3203 |
. . . . . . . . . . . . . 14
 |
| 32 | 31 | dmex 7099 |
. . . . . . . . . . . . 13
 |
| 33 | 32 | dmex 7099 |
. . . . . . . . . . . 12
 |
| 34 | 33 | a1i 11 |
. . . . . . . . . . 11
   



  |
| 35 | 24 | dmeqd 5326 |
. . . . . . . . . . . . 13
   



  |
| 36 | 35 | dmeqd 5326 |
. . . . . . . . . . . 12
   



  |
| 37 | | simpllr 799 |
. . . . . . . . . . . 12
   



  |
| 38 | 36, 37 | eqtr4d 2659 |
. . . . . . . . . . 11
   



  |
| 39 | | simpr 477 |
. . . . . . . . . . . 12
    


    |
| 40 | | simpllr 799 |
. . . . . . . . . . . . . . . . 17
    


    |
| 41 | 40 | fveq2d 6195 |
. . . . . . . . . . . . . . . 16
    


            |
| 42 | | issubc.i |
. . . . . . . . . . . . . . . 16
     |
| 43 | 41, 42 | syl6eqr 2674 |
. . . . . . . . . . . . . . 15
    


       |
| 44 | 43 | fveq1d 6193 |
. . . . . . . . . . . . . 14
    


         
    |
| 45 | | simplr 792 |
. . . . . . . . . . . . . . 15
    


    |
| 46 | 45 | oveqd 6667 |
. . . . . . . . . . . . . 14
    


            |
| 47 | 44, 46 | eleq12d 2695 |
. . . . . . . . . . . . 13
    


              
         |
| 48 | 45 | oveqd 6667 |
. . . . . . . . . . . . . . . 16
    


            |
| 49 | 45 | oveqd 6667 |
. . . . . . . . . . . . . . . . 17
    


            |
| 50 | 40 | fveq2d 6195 |
. . . . . . . . . . . . . . . . . . . . 21
    


  comp  comp    |
| 51 | | issubc.o |
. . . . . . . . . . . . . . . . . . . . 21
comp   |
| 52 | 50, 51 | syl6eqr 2674 |
. . . . . . . . . . . . . . . . . . . 20
    


  comp   |
| 53 | 52 | oveqd 6667 |
. . . . . . . . . . . . . . . . . . 19
    


       comp           |
| 54 | 53 | oveqd 6667 |
. . . . . . . . . . . . . . . . . 18
    


         comp                 |
| 55 | 45 | oveqd 6667 |
. . . . . . . . . . . . . . . . . 18
    


            |
| 56 | 54, 55 | eleq12d 2695 |
. . . . . . . . . . . . . . . . 17
    


          comp         
                |
| 57 | 49, 56 | raleqbidv 3152 |
. . . . . . . . . . . . . . . 16
    


   
            comp         
                      |
| 58 | 48, 57 | raleqbidv 3152 |
. . . . . . . . . . . . . . 15
    


   
                  comp         
                            |
| 59 | 39, 58 | raleqbidv 3152 |
. . . . . . . . . . . . . 14
    


   

                  comp         

                            |
| 60 | 39, 59 | raleqbidv 3152 |
. . . . . . . . . . . . 13
    


   


                  comp         


                            |
| 61 | 47, 60 | anbi12d 747 |
. . . . . . . . . . . 12
    


                                     comp          
       

                             |
| 62 | 39, 61 | raleqbidv 3152 |
. . . . . . . . . . 11
    


   
                                  comp          

       

                             |
| 63 | 34, 38, 62 | sbcied2 3473 |
. . . . . . . . . 10
   



   ![]. ].](_drbrack.gif)                                    comp          

       

                             |
| 64 | 30, 63 | anbi12d 747 |
. . . . . . . . 9
   



  cat 
f     ![]. ].](_drbrack.gif)                                    comp             cat          

     
                       |
| 65 | 64 | adantlr 751 |
. . . . . . . 8
    



   cat  f     ![]. ].](_drbrack.gif) 
                                  comp             cat          

     
                       |
| 66 | 23, 65 | sbcied 3472 |
. . . . . . 7
   


    ![]. ].](_drbrack.gif)  cat 
f     ![]. ].](_drbrack.gif)                                    comp             cat          

     
                       |
| 67 | 22, 66 | syl5bbr 274 |
. . . . . 6
   


    cat 
f     ![]. ].](_drbrack.gif)                                    comp              cat                                         |
| 68 | 67 | ex 450 |
. . . . 5
     
   cat  f     ![]. ].](_drbrack.gif) 
                                  comp              cat                                          |
| 69 | 17, 21, 68 | pm5.21ndd 369 |
. . . 4
     
  cat  f     ![]. ].](_drbrack.gif) 
                                  comp              cat                                         |
| 70 | 3, 69 | sbcied 3472 |
. . 3
 

   ![]. ].](_drbrack.gif)   cat 
f     ![]. ].](_drbrack.gif)                                    comp              cat                                         |
| 71 | 13, 15, 70 | 3bitr2d 296 |
. 2
 

 Subcat   cat 
       

                              |
| 72 | 1, 2, 71 | syl2anc 693 |
1
  Subcat 
 cat                                         |