theorem zltb0 (a b: nat): $ b0 a  a < b $;
    
      
        | Step | Hyp | Ref | Expression | 
|---|
        
          | 1 |  | bitr | (b0 a <Z b0 b <-> odd (a -ZN b)) -> (odd (a -ZN b) <-> a < b) -> (b0 a <Z b0 b <-> a < b) | 
        
          | 2 |  | oddeq | b0 a -Z b0 b = a -ZN b -> (odd (b0 a -Z b0 b) <-> odd (a -ZN b)) | 
        
          | 3 | 2 | conv zlt | b0 a -Z b0 b = a -ZN b -> (b0 a <Z b0 b <-> odd (a -ZN b)) | 
        
          | 4 |  | zsubb0 | b0 a -Z b0 b = a -ZN b | 
        
          | 5 | 3, 4 | ax_mp | b0 a <Z b0 b <-> odd (a -ZN b) | 
        
          | 6 | 1, 5 | ax_mp | (odd (a -ZN b) <-> a < b) -> (b0 a <Z b0 b <-> a < b) | 
        
          | 7 |  | znsubodd | odd (a -ZN b) <-> a < b | 
        
          | 8 | 6, 7 | ax_mp | b0 a <Z b0 b <-> a < b | 
      
    
    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)