下列shape类是一个表示形状的抽象类,area( )为求图形面积的函数,total...答:include<iostream> include<cmath> using namespace std;class Rectangle:public Shape { float x1,x2,y1,y2;public:Rectangle(float argx1=0,float argy1=0,float argx2=0,float argy2=0);float getArea();};Rectangle::Rectangle(float argx1,float argy1,float argx2,float argy2){ x1...