6.12

#include<iostream>
using namespace std;
class area_cl{
protected:
 double height;
 double width;
public:
 area_cl(double r, double s)
 {
height=r;width=s;
 }
 virtual double area()=0;
};
class rectangle:public area_cl{
public:
 rectangle(double r,double s):area_cl(r,s)
 {};
 double area()
 {
 return height*width/2;
 }
};
class isosceles:public area_cl{
public:
 isosceles(double r,double s):area_cl(r,s)
 {};
 double area()
 {
 return height*width;
 }
};
int main()
{
 rectangle rec(4.0,6.0);
 isosceles iso(10.0,5.0);
 area_cl *area1=&rec;
 area_cl *area2=&iso;
 cout<<"三角形面积是"<<area1->area()<<endl<<"矩形面积是"<<area2->area()<<endl;
 system("pause");
 return 0;
}