theorem elnel (a b: nat): $ a e. b <-> odd (shr b a) $;
    
      
        | Step | Hyp | Ref | Expression | 
|---|
        
          | 1 |  | eqidd | _1 = a -> b = b | 
        
          | 2 |  | id | _1 = a -> _1 = a | 
        
          | 3 | 1, 2 | shreqd | _1 = a -> shr b _1 = shr b a | 
        
          | 4 | 3 | oddeqd | _1 = a -> (odd (shr b _1) <-> odd (shr b a)) | 
        
          | 5 | 4 | elabe | a e. {_1 | odd (shr b _1)} <-> odd (shr b a) | 
        
          | 6 | 5 | conv ns | a e. b <-> odd (shr b 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
     (peano2,
      addeq,
      muleq)