theorem rappeq (_F1 _F2: set) (_x1 _x2: nat):
  $ _F1 == _F2 -> _x1 = _x2 -> _F1 @' _x1 == _F2 @' _x2 $;
    
      
        | Step | Hyp | Ref | Expression | 
        
          | 1 | 
           | 
          anl | 
          _F1 == _F2 /\ _x1 = _x2 -> _F1 == _F2  | 
        
        
          | 2 | 
           | 
          anr | 
          _F1 == _F2 /\ _x1 = _x2 -> _x1 = _x2  | 
        
        
          | 3 | 
          1, 2 | 
          rappeqd | 
          _F1 == _F2 /\ _x1 = _x2 -> _F1 @' _x1 == _F2 @' _x2  | 
        
        
          | 4 | 
          3 | 
          exp | 
          _F1 == _F2 -> _x1 = _x2 -> _F1 @' _x1 == _F2 @' _x2  | 
        
      
    
    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)