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function PtInTriang(const P, A, B, C: TPoint): Boolean;

  function _PIT(const C1, C2, C3: TPoint): Boolean;

  begin

   Result := False;

   if (P.x-C1.x)*(C1.y-C2.y) - (P.y-C1.y)*(C1.x-C2.x) >= 0 then

   if (P.x-C2.x)*(C2.y-C3.y) - (P.y-C2.y)*(C2.x-C3.x) >= 0 then

   if (P.x-C3.x)*(C3.y-C1.y) - (P.y-C3.y)*(C3.x-C1.x) >= 0 then

   Result := True;

  end;

 begin

   if (A.x-B.x)*(C.y-B.y) > (A.y-B.y)*(C.x-B.x)

   then Result := _PIT(A, C, B)

   else Result := _PIT(A, B, C);

 end;

function PtinTetragon(P: TPoint; Points: array of TPoint): boolean;

begin

  Result:= PtInTriang(P, Points[0], Points[1], Points[2]) or PtInTriang(P, Points[0], Points[2], Points[3]);

end;

function CrossTetragon(Points1: array of TPoint; Points2: array of TPoint): boolean;

var

  b: boolean;

  i: integer;

begin

  b:= false;

  for I := 0 to 3 do

    if PtinTetragon(Points1[i],Points2) then

      b:= true;

  if not b then

  for I := 0 to 3 do

    if PtinTetragon(Points2[i],Points1) then

      b:= true;

  Result:= b;

end;