根据中心点、半径长度和角度画点

直接上代码： 需要引用 Math 单元。

procedure CenterRadiusPoint(const PX, PY: Integer; const Angle: Double;
  const Radius: Integer; var X, Y: Integer);
var
  AngleHude: Double;
begin
  AngleHude := Angle * PI / 180;  // 角度变成弧度
  X := Round(Radius * Cos(AngleHude)) + PX;
  Y := Round(Radius * Sin(AngleHude)) + PY;
end;

C#版：

        /// 根据中心点、半径、角度，求半径另一端的坐标。注意用的是笛卡尔坐标系  
        /// </summary>  
        /// <param name="center">中心点</param>  
        /// <param name="angle">半径角度</param>  
        /// <param name="radius">半径长度</param>  
        /// <returns>半径另一端的坐标</returns>  
        public static Point CenterRadiusPoint(Point center, double angle, double  radius)  
        {  
            Point p = new Point();  
            double angleHude = angle * Math.PI / 180;/*角度变成弧度*/  
            p.X = (int)(radius * Math.Cos(angleHude)) + center .X;  
            p.Y = (int)(radius * Math.Sin(angleHude)) + center .Y;  
            return p;  
        }    

使用示例：

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Timer1: TTimer;
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure Timer1Timer(Sender: TObject);
  private
    { Private declarations }
    AX, AY: Integer;
    R: Integer;
  public
    { Public declarations }
    procedure Clear();
    procedure CenterRadiusPoint(const PX, PY: Integer; const Angle: Double;
      const Radius: Integer; var X, Y: Integer);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses Math;

procedure TForm1.CenterRadiusPoint(const PX, PY: Integer; const Angle: Double;
  const Radius: Integer; var X, Y: Integer);
var
  AngleHude: Double;
begin
  AngleHude := Angle * PI / 180;  // 角度变成弧度
  X := Round(Radius * Cos(AngleHude)) + PX;
  Y := Round(Radius * Sin(AngleHude)) + PY;
end;

procedure TForm1.Clear;
begin
  Canvas.FillRect(Canvas.ClipRect);
end;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  AX := X;
  AY := Y;
  R := 0;
  Clear();
end;

procedure TForm1.Timer1Timer(Sender: TObject);
var
  I: Integer;
  X, Y: Integer;
  T: Cardinal;
begin
  Inc(R, 8);
  T := GetTickCount;
  for I := 0 to 360 - 1 do begin
    CenterRadiusPoint(AX, AY, I, R, X, Y);
    Canvas.Pixels[X, Y] := 0;
  end;
  T := GetTickCount - T;
  Canvas.TextOut(10, 10, IntToStr(T));
end;

end.