theorem eqmdvdsub3 (a n: nat): $ mod(n): zfst a = zsnd a <-> n || zabs a $;
    
      
        | Step | Hyp | Ref | Expression | 
        
          | 1 | 
           | 
          bitr | 
          (mod(n): zfst a = zsnd a <-> mod(n): zsnd a = zfst a) -> (mod(n): zsnd a = zfst a <-> n || zabs a) -> (mod(n): zfst a = zsnd a <-> n || zabs a)  | 
        
        
          | 2 | 
           | 
          eqmcomb | 
          mod(n): zfst a = zsnd a <-> mod(n): zsnd a = zfst a  | 
        
        
          | 3 | 
          1, 2 | 
          ax_mp | 
          (mod(n): zsnd a = zfst a <-> n || zabs a) -> (mod(n): zfst a = zsnd a <-> n || zabs a)  | 
        
        
          | 4 | 
           | 
          bitr | 
          (mod(n): zsnd a = zfst a <-> n || zabs (zfst a -ZN zsnd a)) -> (n || zabs (zfst a -ZN zsnd a) <-> n || zabs a) -> (mod(n): zsnd a = zfst a <-> n || zabs a)  | 
        
        
          | 5 | 
           | 
          eqmdvdsub2 | 
          mod(n): zsnd a = zfst a <-> n || zabs (zfst a -ZN zsnd a)  | 
        
        
          | 6 | 
          4, 5 | 
          ax_mp | 
          (n || zabs (zfst a -ZN zsnd a) <-> n || zabs a) -> (mod(n): zsnd a = zfst a <-> n || zabs a)  | 
        
        
          | 7 | 
           | 
          dvdeq2 | 
          zabs (zfst a -ZN zsnd a) = zabs a -> (n || zabs (zfst a -ZN zsnd a) <-> n || zabs a)  | 
        
        
          | 8 | 
           | 
          zabseq | 
          zfst a -ZN zsnd a = a -> zabs (zfst a -ZN zsnd a) = zabs a  | 
        
        
          | 9 | 
           | 
          zfstsnd | 
          zfst a -ZN zsnd a = a  | 
        
        
          | 10 | 
          8, 9 | 
          ax_mp | 
          zabs (zfst a -ZN zsnd a) = zabs a  | 
        
        
          | 11 | 
          7, 10 | 
          ax_mp | 
          n || zabs (zfst a -ZN zsnd a) <-> n || zabs a  | 
        
        
          | 12 | 
          6, 11 | 
          ax_mp | 
          mod(n): zsnd a = zfst a <-> n || zabs a  | 
        
        
          | 13 | 
          3, 12 | 
          ax_mp | 
          mod(n): zfst a = zsnd a <-> n || zabs a  | 
        
      
    
    Axiom use
    axs_prop_calc
     (ax_1,
      ax_2,
      ax_3,
      ax_mp,
      itru),
    
axs_pred_calc
     (ax_gen,
      ax_4,
      ax_5,
      ax_6,
      ax_7,
      ax_10,
      ax_11,
      ax_12),
    
axs_set
     (elab,
      ax_8),
    
axs_the
     (theid,
      the0),
    
axs_peano
     (peano1,
      peano2,
      peano5,
      addeq,
      muleq,
      add0,
      addS,
      mul0,
      mulS)