theorem rlistind {x l a: nat} (n: nat) (px: wff x) (p0 pn: wff) (pl: wff l)
  (ps: wff l a):
  $ x = n -> (px <-> pn) $ >
  $ x = 0 -> (px <-> p0) $ >
  $ x = l -> (px <-> pl) $ >
  $ x = l |> a -> (px <-> ps) $ >
  $ p0 $ >
  $ pl -> ps $ >
  $ pn $;
    
      
        | Step | Hyp | Ref | Expression | 
        
          | 1 | 
           | 
          hyp hn | 
          x = n -> (px <-> pn)  | 
        
        
          | 2 | 
           | 
          hyp h0 | 
          x = 0 -> (px <-> p0)  | 
        
        
          | 3 | 
           | 
          hyp hl | 
          x = l -> (px <-> pl)  | 
        
        
          | 4 | 
           | 
          hyp hs | 
          x = l |> a -> (px <-> ps)  | 
        
        
          | 5 | 
           | 
          hyp h1 | 
          p0  | 
        
        
          | 6 | 
          5 | 
          a1i | 
          T. -> p0  | 
        
        
          | 7 | 
           | 
          hyp h2 | 
          pl -> ps  | 
        
        
          | 8 | 
          7 | 
          anwr | 
          T. /\ pl -> ps  | 
        
        
          | 9 | 
          1, 2, 3, 4, 6, 8 | 
          rlistindd | 
          T. -> pn  | 
        
        
          | 10 | 
          9 | 
          trud | 
          pn  | 
        
      
    
    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)