theorem writeeq (_F1 _F2: set) (_a1 _a2 _b1 _b2: nat):
  $ _F1 == _F2 ->
    _a1 = _a2 ->
    _b1 = _b2 ->
    write _F1 _a1 _b1 == write _F2 _a2 _b2 $;
    
      
        | Step | Hyp | Ref | Expression | 
        
          | 1 | 
           | 
          anl | 
          _F1 == _F2 /\ _a1 = _a2 -> _F1 == _F2  | 
        
        
          | 2 | 
          1 | 
          anwl | 
          _F1 == _F2 /\ _a1 = _a2 /\ _b1 = _b2 -> _F1 == _F2  | 
        
        
          | 3 | 
           | 
          anr | 
          _F1 == _F2 /\ _a1 = _a2 -> _a1 = _a2  | 
        
        
          | 4 | 
          3 | 
          anwl | 
          _F1 == _F2 /\ _a1 = _a2 /\ _b1 = _b2 -> _a1 = _a2  | 
        
        
          | 5 | 
           | 
          anr | 
          _F1 == _F2 /\ _a1 = _a2 /\ _b1 = _b2 -> _b1 = _b2  | 
        
        
          | 6 | 
          2, 4, 5 | 
          writeeqd | 
          _F1 == _F2 /\ _a1 = _a2 /\ _b1 = _b2 -> write _F1 _a1 _b1 == write _F2 _a2 _b2  | 
        
        
          | 7 | 
          6 | 
          exp | 
          _F1 == _F2 /\ _a1 = _a2 -> _b1 = _b2 -> write _F1 _a1 _b1 == write _F2 _a2 _b2  | 
        
        
          | 8 | 
          7 | 
          exp | 
          _F1 == _F2 -> _a1 = _a2 -> _b1 = _b2 -> write _F1 _a1 _b1 == write _F2 _a2 _b2  | 
        
      
    
    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)