| Step | Hyp | Ref
| Expression |
| 1 | | fucval.q |
. 2
 FuncCat
  |
| 2 | | df-fuc 16604 |
. . . 4
FuncCat  
                 Nat   
 comp       
           ![]_ ]_](_urbrack.gif)       ![]_ ]_](_urbrack.gif)     Nat        Nat                                    comp                         |
| 3 | 2 | a1i 11 |
. . 3
 FuncCat  
                 Nat   
 comp       
           ![]_ ]_](_urbrack.gif)       ![]_ ]_](_urbrack.gif)     Nat        Nat                                    comp                          |
| 4 | | simprl 794 |
. . . . . . 7
 

    |
| 5 | | simprr 796 |
. . . . . . 7
 

 
  |
| 6 | 4, 5 | oveq12d 6668 |
. . . . . 6
 

        |
| 7 | | fucval.b |
. . . . . 6
   |
| 8 | 6, 7 | syl6eqr 2674 |
. . . . 5
 

      |
| 9 | 8 | opeq2d 4409 |
. . . 4
 

       
            |
| 10 | 4, 5 | oveq12d 6668 |
. . . . . 6
 

   Nat   Nat    |
| 11 | | fucval.n |
. . . . . 6
 Nat   |
| 12 | 10, 11 | syl6eqr 2674 |
. . . . 5
 

   Nat    |
| 13 | 12 | opeq2d 4409 |
. . . 4
 

      
 Nat           |
| 14 | 8 | sqxpeqd 5141 |
. . . . . . 7
 

            |
| 15 | 12 | oveqd 6667 |
. . . . . . . . . 10
 

     Nat          |
| 16 | 12 | oveqd 6667 |
. . . . . . . . . 10
 

     Nat          |
| 17 | 4 | fveq2d 6195 |
. . . . . . . . . . . 12
 

            |
| 18 | | fucval.a |
. . . . . . . . . . . 12
     |
| 19 | 17, 18 | syl6eqr 2674 |
. . . . . . . . . . 11
 

        |
| 20 | 5 | fveq2d 6195 |
. . . . . . . . . . . . . 14
 

  comp  comp    |
| 21 | | fucval.o |
. . . . . . . . . . . . . 14
comp   |
| 22 | 20, 21 | syl6eqr 2674 |
. . . . . . . . . . . . 13
 

  comp   |
| 23 | 22 | oveqd 6667 |
. . . . . . . . . . . 12
 

                       comp                               
           |
| 24 | 23 | oveqd 6667 |
. . . . . . . . . . 11
 

                             comp                                           
                 |
| 25 | 19, 24 | mpteq12dv 4733 |
. . . . . . . . . 10
 

                                  comp                                                                |
| 26 | 15, 16, 25 | mpt2eq123dv 6717 |
. . . . . . . . 9
 

      Nat        Nat                                    comp                                                        
                   |
| 27 | 26 | csbeq2dv 3992 |
. . . . . . . 8
 

        ![]_ ]_](_urbrack.gif)     Nat        Nat                                    comp                          ![]_ ]_](_urbrack.gif)                                     
                   |
| 28 | 27 | csbeq2dv 3992 |
. . . . . . 7
 

        ![]_ ]_](_urbrack.gif)       ![]_ ]_](_urbrack.gif)     Nat        Nat                                    comp                          ![]_ ]_](_urbrack.gif)       ![]_ ]_](_urbrack.gif)                                     
                   |
| 29 | 14, 8, 28 | mpt2eq123dv 6717 |
. . . . . 6
 

                  ![]_ ]_](_urbrack.gif)       ![]_ ]_](_urbrack.gif)     Nat        Nat                                    comp                               ![]_ ]_](_urbrack.gif)       ![]_ ]_](_urbrack.gif)                                     
                    |
| 30 | | fucval.x |
. . . . . . 7
    
      ![]_ ]_](_urbrack.gif)       ![]_ ]_](_urbrack.gif)                                     
                    |
| 31 | 30 | adantr 481 |
. . . . . 6
 

            ![]_ ]_](_urbrack.gif)       ![]_ ]_](_urbrack.gif)                                     
                    |
| 32 | 29, 31 | eqtr4d 2659 |
. . . . 5
 

                  ![]_ ]_](_urbrack.gif)       ![]_ ]_](_urbrack.gif)     Nat        Nat                                    comp                      |
| 33 | 32 | opeq2d 4409 |
. . . 4
 

   comp                   ![]_ ]_](_urbrack.gif)       ![]_ ]_](_urbrack.gif)     Nat        Nat                                    comp                       comp  
  |
| 34 | 9, 13, 33 | tpeq123d 4283 |
. . 3
 

        
          Nat   
 comp       
           ![]_ ]_](_urbrack.gif)       ![]_ ]_](_urbrack.gif)     Nat        Nat                                    comp                      
                 comp      |
| 35 | | fucval.c |
. . 3
   |
| 36 | | fucval.d |
. . 3
   |
| 37 | | tpex 6957 |
. . . 4
                 comp   
 |
| 38 | 37 | a1i 11 |
. . 3
       
      
   comp      |
| 39 | 3, 34, 35, 36, 38 | ovmpt2d 6788 |
. 2
  FuncCat
       
      
   comp      |
| 40 | 1, 39 | syl5eq 2668 |
1
                  comp      |