theorem eqstr2 (A B C: set): $ A == B -> B == C -> C == A $;
    
      
        | Step | Hyp | Ref | Expression | 
|---|
        
          | 1 |  | eqscom | A == C -> C == A | 
        
          | 2 |  | eqstr | A == B -> B == C -> A == C | 
        
          | 3 | 1, 2 | syl6 | A == B -> B == C -> C == A | 
      
    
    Axiom use
    axs_prop_calc
     (ax_1,
      ax_2,
      ax_3,
      ax_mp),
    
axs_pred_calc
     (ax_gen,
      ax_4)