reserve x,y,y1,y2 for set;
reserve G for Group;
reserve a,b,c,d,g,h for Element of G;
reserve A,B,C,D for Subset of G;
reserve H,H1,H2,H3 for Subgroup of G;
reserve n for Nat;
reserve i for Integer;

theorem Th95:
  A in con_class B iff A,B are_conjugated
proof
  thus A in con_class B implies A,B are_conjugated
  proof
    assume A in con_class B;
    then ex C st A = C & B,C are_conjugated;
    hence thesis;
  end;
  assume A,B are_conjugated;
  hence thesis;
end;
