Вывод графика на экран

uses
  GraphABC;
 
function y(x: real): real;
begin
  y := sin(x) + cos(2 * x)
end;
 
const
  a = -pi;
  b = pi;
  h = pi / 25;
  n = round((b - a) / h);
  scale = 50;
var
  x: real;
  i, xc, yc: integer;
begin
  SetWindowSize(round((b - a + 2) * scale), (2 * 2 + 2) * scale);
  xc := WindowWidth div 2;
  yc := WindowHeight div 2;
  Line(xc, WindowHeight - scale div 2, xc, scale div 2);
  Line(scale div 2, yc, WindowWidth - scale div 2, yc);
  for i := -3 to 3 do
    begin
      Line(i * scale + xc, yc, i * scale + xc, yc - scale div 5);
      TextOut(i * scale + xc - scale div 10, yc + scale div 10, IntToStr(i))
    end;
  for i := -2 to 2 do
    if i <> 0 then
      begin
        Line(xc, yc - i * scale, xc + scale div 5, yc - i * scale);
        TextOut(xc - scale div 3, yc - i * scale - scale div 10, IntToStr(i))
      end;
  MoveTo(scale, yc - round(y(a) * scale));
  for i := 1 to n do
    begin
      x := a + h * i;
      LineTo(xc + round(x * scale), yc - round(y(x) * scale))
    end;
  TextOut(scale, scale, 'y = sin(x) + cos(2 * x)')
end.