theorem leupto (a b: nat): $ a <= b <-> upto a <= upto b $;
    
      
        | Step | Hyp | Ref | Expression | 
        
          | 1 | 
           | 
          bitr4 | 
          (a <= b <-> 2 ^ a <= 2 ^ b) -> (upto a <= upto b <-> 2 ^ a <= 2 ^ b) -> (a <= b <-> upto a <= upto b)  | 
        
        
          | 2 | 
           | 
          lepow2 | 
          1 < 2 -> (a <= b <-> 2 ^ a <= 2 ^ b)  | 
        
        
          | 3 | 
           | 
          d1lt2 | 
          1 < 2  | 
        
        
          | 4 | 
          2, 3 | 
          ax_mp | 
          a <= b <-> 2 ^ a <= 2 ^ b  | 
        
        
          | 5 | 
          1, 4 | 
          ax_mp | 
          (upto a <= upto b <-> 2 ^ a <= 2 ^ b) -> (a <= b <-> upto a <= upto b)  | 
        
        
          | 6 | 
           | 
          bitr | 
          (upto a <= upto b <-> upto a + 1 <= upto b + 1) -> (upto a + 1 <= upto b + 1 <-> 2 ^ a <= 2 ^ b) -> (upto a <= upto b <-> 2 ^ a <= 2 ^ b)  | 
        
        
          | 7 | 
           | 
          leadd1 | 
          upto a <= upto b <-> upto a + 1 <= upto b + 1  | 
        
        
          | 8 | 
          6, 7 | 
          ax_mp | 
          (upto a + 1 <= upto b + 1 <-> 2 ^ a <= 2 ^ b) -> (upto a <= upto b <-> 2 ^ a <= 2 ^ b)  | 
        
        
          | 9 | 
           | 
          leeq | 
          upto a + 1 = 2 ^ a -> upto b + 1 = 2 ^ b -> (upto a + 1 <= upto b + 1 <-> 2 ^ a <= 2 ^ b)  | 
        
        
          | 10 | 
           | 
          uptoadd1 | 
          upto a + 1 = 2 ^ a  | 
        
        
          | 11 | 
          9, 10 | 
          ax_mp | 
          upto b + 1 = 2 ^ b -> (upto a + 1 <= upto b + 1 <-> 2 ^ a <= 2 ^ b)  | 
        
        
          | 12 | 
           | 
          uptoadd1 | 
          upto b + 1 = 2 ^ b  | 
        
        
          | 13 | 
          11, 12 | 
          ax_mp | 
          upto a + 1 <= upto b + 1 <-> 2 ^ a <= 2 ^ b  | 
        
        
          | 14 | 
          8, 13 | 
          ax_mp | 
          upto a <= upto b <-> 2 ^ a <= 2 ^ b  | 
        
        
          | 15 | 
          5, 14 | 
          ax_mp | 
          a <= b <-> upto a <= upto 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)