此程序是坐标曲线的编程实现。这段代码基本适合画各种坐标曲线，既可以把原点画在坐标轴上，也可以不画在坐标轴上。-This procedure is programmed coordinate curve. The code base for painting a variety of coordinate curves, the origin can be painted on both axes, it may not draw in the axis.