绘制正弦曲线和余弦曲线

本例效果图:

---

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm1 = class(TForm)
    procedure FormPaint(Sender: TObject);
    procedure FormClick(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

const
  BoolArr: array[Boolean] of string = ('余弦曲线', '正弦曲线');
var
  f: Boolean = True;

procedure TForm1.FormClick(Sender: TObject);
begin
  f := not f;
  Repaint;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  x: Integer;
  y,radian: Double;
begin
  Canvas.Pen.Width := 2;
  Canvas.Pen.Color := clRed;
  Canvas.MoveTo(0, ClientWidth div 2);
  for x := 0 to ClientWidth do
  begin
    radian := x / ClientWidth * 4 * pi;
    if f then y := Sin(radian) else y := Cos(radian);
    y := (1-y) * ClientHeight / 2;
    Canvas.LineTo(Round(x), Round(y));
  end;
  Text := BoolArr[f];
end;

end.