case WM_PAINT: 
        hdc = BeginPaint(hWnd, &ps); 
        // TODO: 在此添加任意繪圖代碼... 
        //畫正玄線 
        #define  PI 3.1415926 
        #define SEGMENT 500 
        int cxClient,cyClient; 
        RECT rect; 
 
        ::GetClientRect(hWnd, &rect); 
        cxClient = rect.right - rect.left; 
        cyClient = rect.bottom - rect.top; 
 
        POINT   pt[SEGMENT]; 
        for (int i=0;i<SEGMENT;i++) 
        { 
            pt[i].x = i * cxClient/SEGMENT;  //cxClient的長度被分成SEGMENT份 
            pt[i].y =  (int)((cyClient/2)*(1 - sin(2 * PI * i/SEGMENT))); //因為sin(2pi)取反，因為數(shù)學坐標Y軸向上，而系統(tǒng)中坐標Y軸向下，+cyClient/2是將坐標原點移到左上角 
        } 
        ::Polyline(hdc, pt, SEGMENT); //繪圖函數(shù) 
 
        EndPaint(hWnd, &ps); 
        break;