theorem b0can (a b: nat): $ b0 a = b0 b <-> a = b $;
    
      
        | Step | Hyp | Ref | Expression | 
|---|
        
          | 1 |  | eqeq | b0 a // 2 = a -> b0 b // 2 = b -> (b0 a // 2 = b0 b // 2 <-> a = b) | 
        
          | 2 |  | b0div2 | b0 a // 2 = a | 
        
          | 3 | 1, 2 | ax_mp | b0 b // 2 = b -> (b0 a // 2 = b0 b // 2 <-> a = b) | 
        
          | 4 |  | b0div2 | b0 b // 2 = b | 
        
          | 5 | 3, 4 | ax_mp | b0 a // 2 = b0 b // 2 <-> a = b | 
        
          | 6 |  | diveq1 | b0 a = b0 b -> b0 a // 2 = b0 b // 2 | 
        
          | 7 | 5, 6 | sylib | b0 a = b0 b -> a = b | 
        
          | 8 |  | b0eq | a = b -> b0 a = b0 b | 
        
          | 9 | 7, 8 | ibii | b0 a = 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)