| Step | Hyp | Ref
| Expression |
| 1 | | nfra1 2941 |
. 2
  
             |
| 2 | | eqeq1 2626 |
. . . . . . . 8
     
       |
| 3 | 2 | rexbidv 3052 |
. . . . . . 7
  
   
        |
| 4 | 3 | 2rexbidv 3057 |
. . . . . 6
  
      
         |
| 5 | 4 | cbvralv 3171 |
. . . . 5
 
           
      
        |
| 6 | | 6nn 11189 |
. . . . . . . . 9
 |
| 7 | 6 | nnzi 11401 |
. . . . . . . 8
 |
| 8 | 7 | a1i 11 |
. . . . . . 7
  Even    |
| 9 | | evenz 41543 |
. . . . . . . . 9
 Even   |
| 10 | | 2z 11409 |
. . . . . . . . . 10
 |
| 11 | 10 | a1i 11 |
. . . . . . . . 9
 Even   |
| 12 | 9, 11 | zaddcld 11486 |
. . . . . . . 8
 Even     |
| 13 | 12 | adantr 481 |
. . . . . . 7
  Even      |
| 14 | | 4cn 11098 |
. . . . . . . . . 10
 |
| 15 | | 2cn 11091 |
. . . . . . . . . 10
 |
| 16 | | 4p2e6 11162 |
. . . . . . . . . . 11
   |
| 17 | 16 | eqcomi 2631 |
. . . . . . . . . 10
   |
| 18 | 14, 15, 17 | mvrraddi 10298 |
. . . . . . . . 9
   |
| 19 | | 2p2e4 11144 |
. . . . . . . . . 10
   |
| 20 | | 2evenALTV 41603 |
. . . . . . . . . . 11
Even |
| 21 | | evenltle 41626 |
. . . . . . . . . . 11
  Even Even 
    |
| 22 | 20, 21 | mp3an2 1412 |
. . . . . . . . . 10
  Even      |
| 23 | 19, 22 | syl5eqbrr 4689 |
. . . . . . . . 9
  Even    |
| 24 | 18, 23 | syl5eqbr 4688 |
. . . . . . . 8
  Even      |
| 25 | | 6re 11101 |
. . . . . . . . . . . 12
 |
| 26 | 25 | a1i 11 |
. . . . . . . . . . 11
 Even   |
| 27 | | 2re 11090 |
. . . . . . . . . . . 12
 |
| 28 | 27 | a1i 11 |
. . . . . . . . . . 11
 Even   |
| 29 | 9 | zred 11482 |
. . . . . . . . . . 11
 Even   |
| 30 | 26, 28, 29 | 3jca 1242 |
. . . . . . . . . 10
 Even     |
| 31 | 30 | adantr 481 |
. . . . . . . . 9
  Even  
   |
| 32 | | lesubadd 10500 |
. . . . . . . . 9
 
   
     |
| 33 | 31, 32 | syl 17 |
. . . . . . . 8
  Even    
     |
| 34 | 24, 33 | mpbid 222 |
. . . . . . 7
  Even      |
| 35 | | eluz2 11693 |
. . . . . . 7
               |
| 36 | 8, 13, 34, 35 | syl3anbrc 1246 |
. . . . . 6
  Even          |
| 37 | | eqeq1 2626 |
. . . . . . . . 9
       
         |
| 38 | 37 | rexbidv 3052 |
. . . . . . . 8
    
   
          |
| 39 | 38 | 2rexbidv 3057 |
. . . . . . 7
    
      
           |
| 40 | 39 | rspcv 3305 |
. . . . . 6
      
 
                        |
| 41 | 36, 40 | syl 17 |
. . . . 5
  Even   
                        |
| 42 | 5, 41 | syl5bi 232 |
. . . 4
  Even   
                        |
| 43 | | nfv 1843 |
. . . . 5
   Even   |
| 44 | | nfre1 3005 |
. . . . 5
  
    |
| 45 | | nfv 1843 |
. . . . . . 7
    Even
   |
| 46 | | nfcv 2764 |
. . . . . . . 8
   |
| 47 | | nfre1 3005 |
. . . . . . . 8
      |
| 48 | 46, 47 | nfrex 3007 |
. . . . . . 7
       |
| 49 | | simplrl 800 |
. . . . . . . . . . . . 13
    Even
    
  |
| 50 | | simplrr 801 |
. . . . . . . . . . . . 13
    Even
    
  |
| 51 | | simpr 477 |
. . . . . . . . . . . . 13
    Even
    
  |
| 52 | 49, 50, 51 | 3jca 1242 |
. . . . . . . . . . . 12
    Even
    

   |
| 53 | 52 | adantr 481 |
. . . . . . . . . . 11
     Even
 
 
 
          |
| 54 | | simp-4l 806 |
. . . . . . . . . . 11
     Even
 
 
 
      Even  |
| 55 | | simpr 477 |
. . . . . . . . . . 11
     Even
 
 
 
              |
| 56 | | mogoldbblem 41629 |
. . . . . . . . . . . 12
    Even       
      |
| 57 | | oveq1 6657 |
. . . . . . . . . . . . . 14
       |
| 58 | 57 | eqeq2d 2632 |
. . . . . . . . . . . . 13
   
     |
| 59 | | oveq2 6658 |
. . . . . . . . . . . . . 14
       |
| 60 | 59 | eqeq2d 2632 |
. . . . . . . . . . . . 13
   
     |
| 61 | 58, 60 | cbvrex2v 3180 |
. . . . . . . . . . . 12
     
     |
| 62 | 56, 61 | sylibr 224 |
. . . . . . . . . . 11
    Even       
      |
| 63 | 53, 54, 55, 62 | syl3anc 1326 |
. . . . . . . . . 10
     Even
 
 
 
            |
| 64 | 63 | exp31 630 |
. . . . . . . . 9
   Even  
 

               |
| 65 | 64 | rexlimdv 3030 |
. . . . . . . 8
   Even  
 
 
     
       |
| 66 | 65 | expr 643 |
. . . . . . 7
   Even 
          
       |
| 67 | 45, 48, 66 | rexlimd 3026 |
. . . . . 6
   Even 
                 |
| 68 | 67 | ex 450 |
. . . . 5
  Even                    |
| 69 | 43, 44, 68 | rexlimd 3026 |
. . . 4
  Even   
               |
| 70 | 42, 69 | syldc 48 |
. . 3
 
              Even  
      |
| 71 | 70 | expd 452 |
. 2
 
             Even
         |
| 72 | 1, 71 | ralrimi 2957 |
1
 
             Even         |