Proof of Theorem cati
| Step | Hyp | Ref
| Expression |
| 1 | | df-cat 10657 |
. . 3
Cat 
                             Ded                                                               
                      |
| 2 | 1 | eleq2i 1541 |
. 2
 Cat
                              Ded                                                               
                       |
| 3 | | cati.1 |
. . . . . . 7
dom   |
| 4 | 3 | domval 10626 |
. . . . . 6
         |
| 5 | 4 | eqcomi 1482 |
. . . . 5
         |
| 6 | 5 | eqeq2i 1488 |
. . . 4
           |
| 7 | | opeq1 2491 |
. . . . . . . 8
         |
| 8 | 7 | opeq1d 2497 |
. . . . . . 7
                
    |
| 9 | 8 | eleq1d 1543 |
. . . . . 6
          
Ded
        
Ded  |
| 10 | | dmeq 3317 |
. . . . . . . . . 10

  |
| 11 | | cati.5 |
. . . . . . . . . 10
 |
| 12 | 10, 11 | syl6eqr 1528 |
. . . . . . . . 9

  |
| 13 | 12 | eleq2d 1544 |
. . . . . . . 8
     |
| 14 | 12 | eleq2d 1544 |
. . . . . . . . . 10
     |
| 15 | 12 | eleq2d 1544 |
. . . . . . . . . . . 12
     |
| 16 | | fveq1 3729 |
. . . . . . . . . . . . . . 15
           |
| 17 | 16 | eqeq1d 1486 |
. . . . . . . . . . . . . 14
                     |
| 18 | | fveq1 3729 |
. . . . . . . . . . . . . . 15
           |
| 19 | 18 | eqeq1d 1486 |
. . . . . . . . . . . . . 14
                     |
| 20 | 17, 19 | anbi12d 630 |
. . . . . . . . . . . . 13
                                         |
| 21 | 20 | imbi1d 615 |
. . . . . . . . . . . 12
                                                                             |
| 22 | 15, 21 | imbi12d 628 |
. . . . . . . . . . 11
                                                                                 |
| 23 | 22 | ralbidv2 1668 |
. . . . . . . . . 10
                                                                                |
| 24 | 14, 23 | imbi12d 628 |
. . . . . . . . 9
   
                                                                                |
| 25 | 24 | ralbidv2 1668 |
. . . . . . . 8
    
                                     

                                       |
| 26 | 13, 25 | imbi12d 628 |
. . . . . . 7
   
                                         

                                        |
| 27 | 26 | ralbidv2 1668 |
. . . . . 6
    
 
                                      

                                       |
| 28 | 9, 27 | anbi12d 630 |
. . . . 5
     
      Ded                                               
      Ded                                            |
| 29 | 12 | raleq1d 1792 |
. . . . . . 7
                                    |
| 30 | 29 | ralbidv 1666 |
. . . . . 6
    
                                   |
| 31 | | fveq1 3729 |
. . . . . . . . . . 11
           |
| 32 | 31 | eqeq1d 1486 |
. . . . . . . . . 10
             |
| 33 | 32 | imbi1d 615 |
. . . . . . . . 9
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