| Step | Hyp | Ref
| Expression |
| 1 | | eleq1w 2684 |
. . . 4
  Word
Word    |
| 2 | | fveq2 6191 |
. . . . 5
           |
| 3 | 2 | eqeq1d 2624 |
. . . 4
                         |
| 4 | 1, 3 | anbi12d 747 |
. . 3
   Word             Word               |
| 5 | 4 | cbvralv 3171 |
. 2
 
 Word
          

 Word              |
| 6 | | reuccats1.1 |
. . . . 5
   |
| 7 | 6 | nfel2 2781 |
. . . 4
   ++       |
| 8 | 6 | nfel2 2781 |
. . . 4
   ++       |
| 9 | | s1eq 13380 |
. . . . . 6
           |
| 10 | 9 | oveq2d 6666 |
. . . . 5
  ++       ++        |
| 11 | 10 | eleq1d 2686 |
. . . 4
   ++       ++         |
| 12 | | s1eq 13380 |
. . . . . 6
           |
| 13 | 12 | oveq2d 6666 |
. . . . 5
  ++       ++        |
| 14 | 13 | eleq1d 2686 |
. . . 4
   ++       ++         |
| 15 | 7, 8, 11, 14 | reu8nf 3516 |
. . 3
   ++         ++         ++     
    |
| 16 | | nfv 1843 |
. . . . 5
 Word  |
| 17 | | nfv 1843 |
. . . . . 6
   Word             |
| 18 | 6, 17 | nfral 2945 |
. . . . 5
    Word             |
| 19 | 16, 18 | nfan 1828 |
. . . 4
   Word   Word              |
| 20 | | nfv 1843 |
. . . . 5
  substr          |
| 21 | 6, 20 | nfreu 3114 |
. . . 4
  
 substr          |
| 22 | | simprl 794 |
. . . . . 6
    Word   Word                ++         ++     
    ++        |
| 23 | | simp-4l 806 |
. . . . . . . . 9
     Word 
 Word
           
   ++     

  ++          Word   |
| 24 | | simpr 477 |
. . . . . . . . 9
     Word 
 Word
           
   ++     

  ++            |
| 25 | 22 | adantr 481 |
. . . . . . . . 9
     Word 
 Word
           
   ++     

  ++           ++        |
| 26 | | simplrr 801 |
. . . . . . . . 9
     Word 
 Word
           
   ++     

  ++          
  ++         |
| 27 | | simp-4r 807 |
. . . . . . . . 9
     Word 
 Word
           
   ++     

  ++          
 Word              |
| 28 | | reuccats1lem 13479 |
. . . . . . . . 9
   Word
 ++      
 
  ++         Word              
 substr          ++         |
| 29 | 23, 24, 25, 26, 27, 28 | syl32anc 1334 |
. . . . . . . 8
     Word 
 Word
           
   ++     

  ++          
 substr          ++         |
| 30 | | oveq1 6657 |
. . . . . . . . . . 11
  ++       substr           ++      substr
          |
| 31 | | simpl 473 |
. . . . . . . . . . . . . . 15
  Word   Word            
Word   |
| 32 | | s1cl 13382 |
. . . . . . . . . . . . . . 15
     Word
  |
| 33 | 31, 32 | anim12i 590 |
. . . . . . . . . . . . . 14
   Word   Word              
Word     Word    |
| 34 | 33 | adantr 481 |
. . . . . . . . . . . . 13
    Word   Word                ++         ++     
    Word     Word
   |
| 35 | 34 | adantr 481 |
. . . . . . . . . . . 12
     Word 
 Word
           
   ++     

  ++          
Word     Word    |
| 36 | | swrdccat1 13457 |
. . . . . . . . . . . 12
  Word     Word    ++      substr
          |
| 37 | 35, 36 | syl 17 |
. . . . . . . . . . 11
     Word 
 Word
           
   ++     

  ++            ++      substr
          |
| 38 | 30, 37 | sylan9eqr 2678 |
. . . . . . . . . 10
      Word   Word            
   ++     

  ++           ++      
 substr           |
| 39 | 38 | eqcomd 2628 |
. . . . . . . . 9
      Word   Word            
   ++     

  ++           ++      

substr           |
| 40 | 39 | ex 450 |
. . . . . . . 8
     Word 
 Word
           
   ++     

  ++            ++       substr            |
| 41 | 29, 40 | impbid 202 |
. . . . . . 7
     Word 
 Word
           
   ++     

  ++          
 substr          ++         |
| 42 | 41 | ralrimiva 2966 |
. . . . . 6
    Word   Word                ++         ++     
    
 substr        
 ++         |
| 43 | | reu6i 3397 |
. . . . . 6
   ++       
 substr        
 ++          substr           |
| 44 | 22, 42, 43 | syl2anc 693 |
. . . . 5
    Word   Word                ++         ++     
     substr           |
| 45 | 44 | exp31 630 |
. . . 4
  Word   Word                 ++     
   ++       


substr             |
| 46 | 19, 21, 45 | rexlimd 3026 |
. . 3
  Word   Word                 ++     
   ++       


substr            |
| 47 | 15, 46 | syl5bi 232 |
. 2
  Word   Word                ++     


substr            |
| 48 | 5, 47 | sylan2b 492 |
1
  Word   Word                ++     


substr            |