定义一个线段类作为矩形的基类，基类有起点和终点坐标，有输出左边和长度以及线段和x轴的夹角的成员函数。矩线段对象的两个坐标作为自己一条边的位置，它具有另外一条边，能输出矩形的4个顶点坐标。给出类的定义并用程序验证它们的功能。-Define a segment class as a rectangular base class, the base class has a beginning and end coordinates, there is a member function of the angle between the output of the left and the length and the line segment and the x axis. The moment two coordinates of a line segment object as a section of its own position, it has also an edge, can output the rectangular coordinates of the vertices of the four. Given in the class definition, and application to verify their function.