theorem ineq0 (A B: set): $ A i^i B == 0 <-> A C_ Compl B $;
    
      
        | Step | Hyp | Ref | Expression | 
|---|
        
          | 1 |  | bitr3 | (A i^i Compl (Compl B) == 0 <-> A i^i B == 0) -> (A i^i Compl (Compl B) == 0 <-> A C_ Compl B) -> (A i^i B == 0 <-> A C_ Compl B) | 
        
          | 2 |  | eqseq1 | A i^i Compl (Compl B) == A i^i B -> (A i^i Compl (Compl B) == 0 <-> A i^i B == 0) | 
        
          | 3 |  | ineq2 | Compl (Compl B) == B -> A i^i Compl (Compl B) == A i^i B | 
        
          | 4 |  | cplcpl | Compl (Compl B) == B | 
        
          | 5 | 3, 4 | ax_mp | A i^i Compl (Compl B) == A i^i B | 
        
          | 6 | 2, 5 | ax_mp | A i^i Compl (Compl B) == 0 <-> A i^i B == 0 | 
        
          | 7 | 1, 6 | ax_mp | (A i^i Compl (Compl B) == 0 <-> A C_ Compl B) -> (A i^i B == 0 <-> A C_ Compl B) | 
        
          | 8 |  | incpleq0 | A i^i Compl (Compl B) == 0 <-> A C_ Compl B | 
        
          | 9 | 7, 8 | ax_mp | A i^i B == 0 <-> A C_ Compl B | 
      
    
    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)