reserve n for Nat;
reserve K for Field;
reserve a,b,c,d,e,f,g,h,i,a1,b1,c1,d1,e1,f1,g1,h1,i1 for Element of K;
reserve M,N for Matrix of 3,K;
reserve p for FinSequence of REAL;

theorem Th01:
  for p,q,r being Point of TOP-REAL 3 holds
  |{p,q,r}| = |{r,p,q}| & |{p,q,r}| = |{q,r,p}|
  proof
    let p,q,r be Point of TOP-REAL 3;
    thus |{p,q,r}| = - |{p,r,q}| by ANPROJ_8:29
                  .= |{r,p,q}| by ANPROJ_8:30;
    thus |{p,q,r}| = - |{q,p,r}| by ANPROJ_8:30
                  .= |{q,r,p}| by ANPROJ_8:29;
  end;
