function d(A,B : TPunkt) : real;
  begin
    result := sqrt(sqr(B.X-A.X)+sqr(B.Y-A.Y));
  end;

  function winkel(P,S,W : TPunkt) : real;
  var
    a,b,c,cosa : real;
  begin
    a := d(P,W); b := d(W,S); c := d(S,P);
    if b*c  0 then
    begin
      cosa := (b*b+c*c-a*a)/(2*b*c);
      if abs(cosa)