theorem Arroweq (_A1 _A2 _B1 _B2: set):
  $ _A1 == _A2 -> _B1 == _B2 -> Arrow _A1 _B1 == Arrow _A2 _B2 $;
    
      
        | Step | Hyp | Ref | Expression | 
        
          | 1 | 
           | 
          anl | 
          _A1 == _A2 /\ _B1 == _B2 -> _A1 == _A2  | 
        
        
          | 2 | 
           | 
          anr | 
          _A1 == _A2 /\ _B1 == _B2 -> _B1 == _B2  | 
        
        
          | 3 | 
          1, 2 | 
          Arroweqd | 
          _A1 == _A2 /\ _B1 == _B2 -> Arrow _A1 _B1 == Arrow _A2 _B2  | 
        
        
          | 4 | 
          3 | 
          exp | 
          _A1 == _A2 -> _B1 == _B2 -> Arrow _A1 _B1 == Arrow _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)