theorem pi22pr (a b c: nat): $ pi22 (a, b, c) = c $;
    
      
        | Step | Hyp | Ref | Expression | 
        
          | 1 | 
           | 
          eqtr | 
          pi22 (a, b, c) = snd (b, c) -> snd (b, c) = c -> pi22 (a, b, c) = c  | 
        
        
          | 2 | 
           | 
          sndeq | 
          snd (a, b, c) = b, c -> snd (snd (a, b, c)) = snd (b, c)  | 
        
        
          | 3 | 
          2 | 
          conv pi22 | 
          snd (a, b, c) = b, c -> pi22 (a, b, c) = snd (b, c)  | 
        
        
          | 4 | 
           | 
          sndpr | 
          snd (a, b, c) = b, c  | 
        
        
          | 5 | 
          3, 4 | 
          ax_mp | 
          pi22 (a, b, c) = snd (b, c)  | 
        
        
          | 6 | 
          1, 5 | 
          ax_mp | 
          snd (b, c) = c -> pi22 (a, b, c) = c  | 
        
        
          | 7 | 
           | 
          sndpr | 
          snd (b, c) = c  | 
        
        
          | 8 | 
          6, 7 | 
          ax_mp | 
          pi22 (a, b, c) = c  | 
        
      
    
    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)