Нарисовать график функции y=cos2x

uses graphABC;
function F(x:real):real;
begin
F:=cos(2*x);
end;
 
var xn,xk,x,mx,dx:real;
    x0,y0,my,i:integer;
    s:string;
begin
x0:=windowwidth div 2;{öåíòð ýêðàíà}
y0:=windowheight div 2;
xn:=-2*pi;xk:=2*pi;{èíòåðâàë ïî Õ}
mx:=(x0-30)/xk;{ìàñøòàá ïî Õ}
my:=y0-40;{ïî Ó}
{ãðàôèê}
x:=xn;
dx:=0.001;
while x<=xk do
 begin
  x:=x+dx; {íàðàùèâàåì õ}
  setpixel(x0+round(x*mx),y0-round(F(x)*my),clBlue);
 end;
line(0,y0,windowwidth,y0);{îñè}
line(windowwidth,y0,windowwidth-10,y0+5);
line(windowwidth,y0,windowwidth-10,y0-5);
line(x0,0,X0,windowheight);
line(x0,0,x0-5,10);
line(x0,0,x0+5,10);
textout(x0+5,y0+10,'0');
{ïîäïèñè êîíöîâ îñåé}
textout(windowwidth-10,y0-20,'X');
textout(x0+10,0, 'Y');
setfontsize(12);
 
textout(x0-120,30,'F(x)=cos(2x)');
end.