知道线的起点，长度，与x轴的夹角，如何使用程序编程画线？

 [CommandMethod("DrawLineTest")]
  public void DrawLineTest()
  {
   double angle = Math.PI / 4;//与X轴夹角
   Point3d startPoint = new Point3d(0,0,0);//起点
   double lineLength = 50;//线的长度
   Vector3d vector = new Vector3d(1, 0, 0);//x轴方向向量
   Point3d endPoint = startPoint + (vector.GetNormal().RotateBy(angle,Vector3d.ZAxis)) * lineLength;
   //把x轴向量转到指定角度就可以了 
   Line line = new Line(startPoint, endPoint);
   AddEntity(line);
  }
public void AddEntity(Entity entity)
  {
   Document doc = AcadApp.DocumentManager.MdiActiveDocument;
   Database db = doc.Database;
   using (Transaction trans = db.TransactionManager.StartTransaction()) {
    BlockTable bt = (trans.GetObject(db.BlockTableId, OpenMode.ForWrite)) as BlockTable;
    BlockTableRecord btr = (trans.GetObject(bt[BlockTableRecord.ModelSpace], OpenMode.ForWrite)) as BlockTableRecord;
   
    ObjectId objectId = btr.AppendEntity(entity);
    trans.AddNewlyCreatedDBObject(entity, true);
    trans.Commit();
    trans.Dispose();
   }
  }

(defun c:hx()
  (setq jd (getreal "\n角度:"))
  (setq cd (getreal "\n长度:"))
  (setq p1 (getpoint "\n起点:"))
  (setq p2 (* (cos (* pi (/ jd 180))) cd))
  (setq p3 (* (sin (* pi (/ jd 180))) cd))
  (setq p2 (+ (car p1) p2))
  (setq p3 (+ (cadr p1) p3))
    (command "line" p1 (list p2 p3) "")
    (princ)
  )