| Step | Hyp | Ref
| Expression |
| 1 | | eleq1w 2268 |
. . . 4
  Word
Word    |
| 2 | | fveqeq2 5608 |
. . . 4
  ♯   ♯   ♯   ♯      |
| 3 | 1, 2 | anbi12d 473 |
. . 3
   Word ♯   ♯     Word ♯   ♯       |
| 4 | 3 | cbvralvw 2746 |
. 2
 
 Word
♯   ♯      Word ♯   ♯      |
| 5 | | reuccatpfxs1.1 |
. . . . 5
   |
| 6 | 5 | nfel2 2363 |
. . . 4
   ++       |
| 7 | 5 | nfel2 2363 |
. . . 4
   ++       |
| 8 | | s1eq 11111 |
. . . . . 6
           |
| 9 | 8 | oveq2d 5983 |
. . . . 5
  ++       ++        |
| 10 | 9 | eleq1d 2276 |
. . . 4
   ++       ++         |
| 11 | | s1eq 11111 |
. . . . . 6
           |
| 12 | 11 | oveq2d 5983 |
. . . . 5
  ++       ++        |
| 13 | 12 | eleq1d 2276 |
. . . 4
   ++       ++         |
| 14 | 6, 7, 10, 13 | reu8nf 3087 |
. . 3
   ++         ++         ++     
    |
| 15 | | nfv 1552 |
. . . . 5
 Word  |
| 16 | | nfv 1552 |
. . . . . 6
   Word ♯   ♯     |
| 17 | 5, 16 | nfralw 2545 |
. . . . 5
    Word ♯   ♯     |
| 18 | 15, 17 | nfan 1589 |
. . . 4
   Word   Word ♯   ♯      |
| 19 | | nfv 1552 |
. . . . 5
  prefix ♯    |
| 20 | 5, 19 | nfreuw 2683 |
. . . 4
  
 prefix ♯    |
| 21 | | simprl 529 |
. . . . . 6
    Word   Word ♯   ♯    
   ++     

  ++          ++        |
| 22 | | simpl 109 |
. . . . . . . . . . 11
  Word   Word ♯   ♯     Word   |
| 23 | 22 | ad2antrr 488 |
. . . . . . . . . 10
    Word   Word ♯   ♯    
   ++     

  ++         Word   |
| 24 | 23 | anim1i 340 |
. . . . . . . . 9
     Word 
 Word
♯   ♯        ++         ++     
   
 Word    |
| 25 | | simplrr 536 |
. . . . . . . . 9
     Word 
 Word
♯   ♯        ++         ++     
   

  ++         |
| 26 | | simp-4r 542 |
. . . . . . . . 9
     Word 
 Word
♯   ♯        ++         ++     
   

 Word ♯   ♯      |
| 27 | | reuccatpfxs1lem 11237 |
. . . . . . . . 9
   Word


  ++         Word ♯   ♯       prefix ♯  
 ++
        |
| 28 | 24, 25, 26, 27 | syl3anc 1250 |
. . . . . . . 8
     Word 
 Word
♯   ♯        ++         ++     
   
  prefix ♯  
 ++         |
| 29 | | oveq1 5974 |
. . . . . . . . . . 11
  ++       prefix ♯     ++      prefix
♯     |
| 30 | | s1cl 11113 |
. . . . . . . . . . . . . 14
     Word
  |
| 31 | 22, 30 | anim12i 338 |
. . . . . . . . . . . . 13
   Word   Word ♯   ♯      
Word     Word    |
| 32 | 31 | ad2antrr 488 |
. . . . . . . . . . . 12
     Word 
 Word
♯   ♯        ++         ++     
   
 Word     Word
   |
| 33 | | pfxccat1 11193 |
. . . . . . . . . . . 12
  Word     Word    ++      prefix
♯     |
| 34 | 32, 33 | syl 14 |
. . . . . . . . . . 11
     Word 
 Word
♯   ♯        ++         ++     
   
  ++      prefix
♯     |
| 35 | 29, 34 | sylan9eqr 2262 |
. . . . . . . . . 10
      Word   Word ♯   ♯        ++         ++     
   
 ++
       prefix
♯     |
| 36 | 35 | eqcomd 2213 |
. . . . . . . . 9
      Word   Word ♯   ♯        ++         ++     
   
 ++
     
 prefix ♯     |
| 37 | 36 | ex 115 |
. . . . . . . 8
     Word 
 Word
♯   ♯        ++         ++     
   
  ++       prefix ♯      |
| 38 | 28, 37 | impbid 129 |
. . . . . . 7
     Word 
 Word
♯   ♯        ++         ++     
   
  prefix ♯  
 ++
        |
| 39 | 38 | ralrimiva 2581 |
. . . . . 6
    Word   Word ♯   ♯    
   ++     

  ++         
  prefix ♯  
 ++
        |
| 40 | | reu6i 2971 |
. . . . . 6
   ++       
 prefix ♯  
 ++          prefix ♯     |
| 41 | 21, 39, 40 | syl2anc 411 |
. . . . 5
    Word   Word ♯   ♯    
   ++     

  ++         
 prefix ♯     |
| 42 | 41 | exp31 364 |
. . . 4
  Word   Word ♯   ♯         ++     
   ++       


prefix ♯       |
| 43 | 18, 20, 42 | rexlimd 2622 |
. . 3
  Word   Word ♯   ♯      
  ++     

  ++       


prefix ♯      |
| 44 | 14, 43 | biimtrid 152 |
. 2
  Word   Word ♯   ♯      
 ++
     
 prefix ♯      |
| 45 | 4, 44 | sylan2b 287 |
1
  Word   Word ♯   ♯      
 ++
     
 prefix ♯      |