reserve A,B,C,D,E,F,G for Point of TOP-REAL 2;

theorem Th6:
  angle(C,B,A) < PI implies 0 <= the_diameter_of_the_circumcircle(A,B,C)
  proof
    assume angle(C,B,A) < PI;
    then 0 <= the_area_of_polygon3(A,B,C) by Th5;
    hence thesis;
  end;
