运用面向对象方法设计点类和平面图形类（含点类成员），并由后者

派生设计圆类（含圆心、半径）、正方形类（含左上角顶点、边长）与矩形类（含

左上角顶点、长和宽）、三角形类（含三个顶点）；同时为有关类设计构造函数、

成员数据设置/提取操作函数、顶点显示函数及周长与面积计算函数，其中顶点

显示函数及周长与面积计算函数在平面图形类中应定义为纯虚函数。在主函数

第 4 页

中，分别创建各类对象，调用和执行相关成员函数，观察并分析程序运行结果-The use of object-oriented methods and graphic design point class graphics classes (including Point class members), derived by the latter design round classes (including center, radius), square type (including upper left vertex, edge length) with the rectangular type (including left corner vertices, length and width), triangles class (with three vertices)　while designing the relevant class constructor member data set/extraction operation function, the vertex display functions and girth and area calculation function, where the vertex functions and week display length and area calculation function in the graphic class should be defined as a pure virtual function. In the first four in the main function, namely to create all kinds of objects, invoke and execute the relevant member functions, observe and analyze the result of the program