绘制sin曲线

sinView.cppvoid CSinView::OnRed() {    // TODO: Add your command handler code here    CDC *pDC = GetDC();  //获取窗口设备环境    CPen NewPen;      NewPen.CreatePen(PS_SOLID, 2, RGB(255, 0, 0));  //红色实线    CPen *pOldPen = pDC->SelectObject(&NewPen);    pDC->MoveTo(20, yCenter);  //坐标原点为(20， yCenter)    int y, x;    double dy;    for(int i=5; i<nRight; i+=5)    {        x = 20 + i;        dy = (yCenter - 20) * sin(i*4*3.14159/(nRight-45));  //sin为弧度，不是角度        y = yCenter - (int)dy;        pDC->LineTo(x, y);        pDC->MoveTo(x, y);    }    pDC->SelectObject(pOldPen);    NewPen.DeleteObject();}