Proof of Theorem sgnmul
| Step | Hyp | Ref
| Expression |
| 1 | | remulcl 10021 |
. . 3
 
     |
| 2 | 1 | rexrd 10089 |
. 2
 
     |
| 3 | | eqeq1 2626 |
. 2
 sgn   
 sgn     sgn  sgn    sgn  sgn      |
| 4 | | eqeq1 2626 |
. 2
 sgn   
 sgn     sgn  sgn    sgn  sgn      |
| 5 | | eqeq1 2626 |
. 2
 sgn      sgn     sgn  sgn  
  sgn  sgn      |
| 6 | | fveq2 6191 |
. . . . . . 7
 sgn  sgn    |
| 7 | | sgn0 13829 |
. . . . . . 7
sgn   |
| 8 | 6, 7 | syl6eq 2672 |
. . . . . 6
 sgn    |
| 9 | 8 | oveq1d 6665 |
. . . . 5
  sgn  sgn    sgn     |
| 10 | 9 | adantl 482 |
. . . 4
     
 
  sgn  sgn    sgn     |
| 11 | | sgnclre 30601 |
. . . . . . 7
 sgn    |
| 12 | 11 | recnd 10068 |
. . . . . 6
 sgn    |
| 13 | 12 | mul02d 10234 |
. . . . 5
  sgn     |
| 14 | 13 | ad3antlr 767 |
. . . 4
     
 
  sgn     |
| 15 | 10, 14 | eqtr2d 2657 |
. . 3
     
 
  sgn  sgn     |
| 16 | | fveq2 6191 |
. . . . . . 7
 sgn  sgn    |
| 17 | 16, 7 | syl6eq 2672 |
. . . . . 6
 sgn    |
| 18 | 17 | oveq2d 6666 |
. . . . 5
  sgn  sgn    sgn     |
| 19 | 18 | adantl 482 |
. . . 4
     
 
  sgn  sgn    sgn     |
| 20 | | sgnclre 30601 |
. . . . . . 7
 sgn    |
| 21 | 20 | recnd 10068 |
. . . . . 6
 sgn    |
| 22 | 21 | mul01d 10235 |
. . . . 5
  sgn     |
| 23 | 22 | ad3antrrr 766 |
. . . 4
     
 
  sgn     |
| 24 | 19, 23 | eqtr2d 2657 |
. . 3
     
 
  sgn  sgn     |
| 25 | | simpl 473 |
. . . . . 6
 
   |
| 26 | 25 | recnd 10068 |
. . . . 5
 
   |
| 27 | | simpr 477 |
. . . . . 6
 
   |
| 28 | 27 | recnd 10068 |
. . . . 5
 
   |
| 29 | 26, 28 | mul0ord 10677 |
. . . 4
 
         |
| 30 | 29 | biimpa 501 |
. . 3
      
    |
| 31 | 15, 24, 30 | mpjaodan 827 |
. 2
      
 sgn  sgn     |
| 32 | | simpll 790 |
. . . 4
    
 
  |
| 33 | 32 | rexrd 10089 |
. . 3
    
 
  |
| 34 | | oveq1 6657 |
. . . 4
 sgn 
 sgn  sgn    sgn     |
| 35 | 34 | eqeq2d 2632 |
. . 3
 sgn 
  sgn  sgn  
 sgn      |
| 36 | | oveq1 6657 |
. . . 4
 sgn 
 sgn  sgn    sgn     |
| 37 | 36 | eqeq2d 2632 |
. . 3
 sgn 
  sgn  sgn  
 sgn      |
| 38 | | oveq1 6657 |
. . . 4
 sgn    sgn  sgn     sgn     |
| 39 | 38 | eqeq2d 2632 |
. . 3
 sgn     sgn  sgn     sgn      |
| 40 | | simpr 477 |
. . . 4
        
  |
| 41 | 26 | adantr 481 |
. . . . . . 7
    
 
  |
| 42 | 28 | adantr 481 |
. . . . . . 7
    
 
  |
| 43 | | simpr 477 |
. . . . . . . 8
    
 
    |
| 44 | 43 | gt0ne0d 10592 |
. . . . . . 7
    
 
    |
| 45 | 41, 42, 44 | mulne0bad 10682 |
. . . . . 6
    
 
  |
| 46 | 45 | neneqd 2799 |
. . . . 5
    
 
  |
| 47 | 46 | adantr 481 |
. . . 4
        
  |
| 48 | 40, 47 | pm2.21dd 186 |
. . 3
          sgn     |
| 49 | 27 | ad2antrr 762 |
. . . . . . 7
           |
| 50 | 49 | rexrd 10089 |
. . . . . 6
           |
| 51 | | simpll 790 |
. . . . . . 7
         
   |
| 52 | | 0red 10041 |
. . . . . . . 8
           |
| 53 | | simplll 798 |
. . . . . . . 8
           |
| 54 | | simpr 477 |
. . . . . . . 8
           |
| 55 | 52, 53, 54 | ltled 10185 |
. . . . . . 7
           |
| 56 | | simplr 792 |
. . . . . . 7
             |
| 57 | | prodgt0 10868 |
. . . . . . 7
     
     |
| 58 | 51, 55, 56, 57 | syl12anc 1324 |
. . . . . 6
           |
| 59 | | sgnp 13830 |
. . . . . 6
   sgn    |
| 60 | 50, 58, 59 | syl2anc 693 |
. . . . 5
         sgn    |
| 61 | 60 | oveq2d 6666 |
. . . 4
          sgn       |
| 62 | | 1t1e1 11175 |
. . . 4
   |
| 63 | 61, 62 | syl6req 2673 |
. . 3
          sgn     |
| 64 | 27 | ad2antrr 762 |
. . . . . . 7
           |
| 65 | 64 | rexrd 10089 |
. . . . . 6
           |
| 66 | | simplll 798 |
. . . . . . . . 9
           |
| 67 | 66 | renegcld 10457 |
. . . . . . . 8
            |
| 68 | 64 | renegcld 10457 |
. . . . . . . 8
            |
| 69 | | 0red 10041 |
. . . . . . . . 9
           |
| 70 | | simpr 477 |
. . . . . . . . . 10
           |
| 71 | 25 | lt0neg1d 10597 |
. . . . . . . . . . 11
 
      |
| 72 | 71 | ad2antrr 762 |
. . . . . . . . . 10
         
    |
| 73 | 70, 72 | mpbid 222 |
. . . . . . . . 9
            |
| 74 | 69, 67, 73 | ltled 10185 |
. . . . . . . 8
            |
| 75 | | simplr 792 |
. . . . . . . . 9
             |
| 76 | 26 | ad2antrr 762 |
. . . . . . . . . 10
           |
| 77 | 28 | ad2antrr 762 |
. . . . . . . . . 10
           |
| 78 | 76, 77 | mul2negd 10485 |
. . . . . . . . 9
                 |
| 79 | 75, 78 | breqtrrd 4681 |
. . . . . . . 8
               |
| 80 | | prodgt0 10868 |
. . . . . . . 8
      
      
   |
| 81 | 67, 68, 74, 79, 80 | syl22anc 1327 |
. . . . . . 7
            |
| 82 | 27 | lt0neg1d 10597 |
. . . . . . . 8
 
      |
| 83 | 82 | ad2antrr 762 |
. . . . . . 7
         
    |
| 84 | 81, 83 | mpbird 247 |
. . . . . 6
           |
| 85 | | sgnn 13834 |
. . . . . 6
   sgn     |
| 86 | 65, 84, 85 | syl2anc 693 |
. . . . 5
         sgn     |
| 87 | 86 | oveq2d 6666 |
. . . 4
           sgn         |
| 88 | | neg1mulneg1e1 11245 |
. . . 4
     |
| 89 | 87, 88 | syl6req 2673 |
. . 3
           sgn     |
| 90 | 33, 35, 37, 39, 48, 63, 89 | sgn3da 30603 |
. 2
    
 
 sgn  sgn     |
| 91 | | simpll 790 |
. . . 4
      
  |
| 92 | 91 | rexrd 10089 |
. . 3
      
  |
| 93 | 34 | eqeq2d 2632 |
. . 3
 sgn 
   sgn  sgn  
  sgn      |
| 94 | 36 | eqeq2d 2632 |
. . 3
 sgn 
   sgn  sgn  
  sgn      |
| 95 | 38 | eqeq2d 2632 |
. . 3
 sgn      sgn  sgn      sgn      |
| 96 | | simpr 477 |
. . . 4
     
  
  |
| 97 | 26 | ad2antrr 762 |
. . . . . 6
     
  
  |
| 98 | 28 | ad2antrr 762 |
. . . . . 6
     
  
  |
| 99 | | simplr 792 |
. . . . . . 7
     
    
  |
| 100 | 99 | lt0ne0d 10593 |
. . . . . 6
     
       |
| 101 | 97, 98, 100 | mulne0bad 10682 |
. . . . 5
     
     |
| 102 | 101 | neneqd 2799 |
. . . 4
     
  
  |
| 103 | 96, 102 | pm2.21dd 186 |
. . 3
     
     sgn     |
| 104 | 27 | ad2antrr 762 |
. . . . . . 7
     
     |
| 105 | 104 | rexrd 10089 |
. . . . . 6
     
     |
| 106 | | simplr 792 |
. . . . . . 7
      
  |
| 107 | 26, 28 | mulcomd 10061 |
. . . . . . . . 9
 
       |
| 108 | 107 | breq1d 4663 |
. . . . . . . 8
 
         |
| 109 | 108 | biimpa 501 |
. . . . . . 7
      
    |
| 110 | 106, 91, 109 | mul2lt0rgt0 11933 |
. . . . . 6
     
     |
| 111 | 105, 110,
85 | syl2anc 693 |
. . . . 5
     
   sgn     |
| 112 | 111 | oveq2d 6666 |
. . . 4
     
    sgn        |
| 113 | | neg1cn 11124 |
. . . . 5
  |
| 114 | 113 | mulid2i 10043 |
. . . 4
     |
| 115 | 112, 114 | syl6req 2673 |
. . 3
     
     sgn     |
| 116 | 106 | adantr 481 |
. . . . . . 7
     
     |
| 117 | 116 | rexrd 10089 |
. . . . . 6
     
     |
| 118 | 106, 91, 109 | mul2lt0rlt0 11932 |
. . . . . 6
     
     |
| 119 | 117, 118,
59 | syl2anc 693 |
. . . . 5
     
   sgn    |
| 120 | 119 | oveq2d 6666 |
. . . 4
     
     sgn        |
| 121 | 113 | mulid1i 10042 |
. . . 4
     |
| 122 | 120, 121 | syl6req 2673 |
. . 3
     
      sgn     |
| 123 | 92, 93, 94, 95, 103, 115, 122 | sgn3da 30603 |
. 2
      
  sgn  sgn     |
| 124 | 2, 3, 4, 5, 31, 90, 123 | sgn3da 30603 |
1
 
 sgn     sgn  sgn     |