Proof of Theorem topgrpi
| Step | Hyp | Ref
| Expression |
| 1 | | df-topgrp 14970 |
. . 3
TopGrp       Grp Top     Cn  inv   Cn     |
| 2 | 1 | eleq2i 1961 |
. 2

TopGrp       Grp Top     Cn  inv   Cn      |
| 3 | | topgrpi.1 |
. . . 4
     |
| 4 | | eqtr3 1907 |
. . . . . 6
             |
| 5 | 4 | eqcomd 1889 |
. . . . 5
             |
| 6 | | eleq1 1957 |
. . . . . . 7
  Grp Grp  |
| 7 | 6 | anbi1d 679 |
. . . . . 6
   Grp Top  Grp
Top   |
| 8 | | eleq1 1957 |
. . . . . 6
      Cn
     Cn     |
| 9 | | fveq2 4681 |
. . . . . . . 8
 inv  inv    |
| 10 | | topgrpi.3 |
. . . . . . . 8
inv   |
| 11 | 9, 10 | syl6eqr 1946 |
. . . . . . 7
 inv    |
| 12 | 11 | eleq1d 1963 |
. . . . . 6
  inv   Cn   Cn     |
| 13 | 7, 8, 12 | 3anbi123d 1168 |
. . . . 5
    Grp Top     Cn  inv   Cn     Grp Top
    Cn
  Cn      |
| 14 | 5, 13 | syl 12 |
. . . 4
              Grp
Top
    Cn  inv   Cn     Grp Top
    Cn   Cn      |
| 15 | 3, 14 | mpan 759 |
. . 3
        Grp Top     Cn  inv   Cn     Grp Top
    Cn
  Cn      |
| 16 | | topgrpi.2 |
. . . 4
     |
| 17 | | eqtr3 1907 |
. . . . . 6
             |
| 18 | 17 | eqcomd 1889 |
. . . . 5
             |
| 19 | | eleq1 1957 |
. . . . . . 7
  Top Top  |
| 20 | 19 | anbi2d 678 |
. . . . . 6
   Grp Top  Grp
Top   |
| 21 | | opreq12 4891 |
. . . . . . . . 9
           |
| 22 | 21 | anidms 480 |
. . . . . . . 8
         |
| 23 | | opreq12 4891 |
. . . . . . . 8
             Cn      Cn    |
| 24 | 22, 23 | mpancom 769 |
. . . . . . 7
     Cn      Cn    |
| 25 | 24 | eleq2d 1964 |
. . . . . 6
      Cn
     Cn     |
| 26 | | opreq12 4891 |
. . . . . . . 8
    Cn   Cn    |
| 27 | 26 | anidms 480 |
. . . . . . 7
  Cn   Cn    |
| 28 | 27 | eleq2d 1964 |
. . . . . 6
   Cn   Cn     |
| 29 | 20, 25, 28 | 3anbi123d 1168 |
. . . . 5
    Grp Top     Cn   Cn     Grp Top     Cn 
 Cn
     |
| 30 | 18, 29 | syl 12 |
. . . 4
              Grp
Top
    Cn   Cn     Grp
Top
    Cn   Cn      |
| 31 | 16, 30 | mpan 759 |
. . 3
        Grp Top     Cn   Cn     Grp Top     Cn 
 Cn
     |
| 32 | 15, 31 | elopabi 5059 |
. 2

  
   Grp Top     Cn  inv   Cn      Grp Top
    Cn   Cn     |
| 33 | 2, 32 | sylbi 216 |
1

TopGrp   Grp Top
    Cn   Cn     |