theorem funceqd (_G: wff) (_F1 _F2 _A1 _A2 _B1 _B2: set):
  $ _G -> _F1 == _F2 $ >
  $ _G -> _A1 == _A2 $ >
  $ _G -> _B1 == _B2 $ >
  $ _G -> (func _F1 _A1 _B1 <-> func _F2 _A2 _B2) $;
    
      
        | Step | Hyp | Ref | Expression | 
|---|
        
          | 1 |  | hyp _Fh | _G -> _F1 == _F2 | 
        
          | 2 | 1 | isfeqd | _G -> (isfun _F1 <-> isfun _F2) | 
        
          | 3 | 1 | dmeqd | _G -> Dom _F1 == Dom _F2 | 
        
          | 4 |  | hyp _Ah | _G -> _A1 == _A2 | 
        
          | 5 | 3, 4 | eqseqd | _G -> (Dom _F1 == _A1 <-> Dom _F2 == _A2) | 
        
          | 6 | 2, 5 | aneqd | _G -> (isfun _F1 /\ Dom _F1 == _A1 <-> isfun _F2 /\ Dom _F2 == _A2) | 
        
          | 7 | 1 | rneqd | _G -> Ran _F1 == Ran _F2 | 
        
          | 8 |  | hyp _Bh | _G -> _B1 == _B2 | 
        
          | 9 | 7, 8 | sseqd | _G -> (Ran _F1 C_ _B1 <-> Ran _F2 C_ _B2) | 
        
          | 10 | 6, 9 | aneqd | _G -> (isfun _F1 /\ Dom _F1 == _A1 /\ Ran _F1 C_ _B1 <-> isfun _F2 /\ Dom _F2 == _A2 /\ Ran _F2 C_ _B2) | 
        
          | 11 | 10 | conv func | _G -> (func _F1 _A1 _B1 <-> func _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)