theorem prltsuc (a b: nat): $ a, b < suc (a + b), 0 $;
    
      
        | Step | Hyp | Ref | Expression | 
|---|
        
          | 1 |  | ltnle | a, b < suc (a + b), 0 <-> ~suc (a + b), 0 <= a, b | 
        
          | 2 |  | prlem2 | suc (a + b), 0 <= a, b -> suc (a + b) + 0 <= a + b | 
        
          | 3 |  | ltnle | a + b < suc (a + b) + 0 <-> ~suc (a + b) + 0 <= a + b | 
        
          | 4 |  | lteq2 | suc (a + b) + 0 = suc (a + b) -> (a + b < suc (a + b) + 0 <-> a + b < suc (a + b)) | 
        
          | 5 |  | add0 | suc (a + b) + 0 = suc (a + b) | 
        
          | 6 | 4, 5 | ax_mp | a + b < suc (a + b) + 0 <-> a + b < suc (a + b) | 
        
          | 7 |  | ltsucid | a + b < suc (a + b) | 
        
          | 8 | 6, 7 | mpbir | a + b < suc (a + b) + 0 | 
        
          | 9 | 3, 8 | mpbi | ~suc (a + b) + 0 <= a + b | 
        
          | 10 | 2, 9 | mt | ~suc (a + b), 0 <= a, b | 
        
          | 11 | 1, 10 | mpbir | a, b < suc (a + b), 0 | 
      
    
    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)