#include <iostream>
#include <cmath>
using namespace std;
class Point
{
public:
    Point(double x=0,double y=0);
    void setPoint(double,double);
    double getx()
    {
        return x;
    }
    double gety()
    {
        return y;
    }
    void display();
protected:
    double x,y;
};
class Circle:public Point
{
public:
    Circle(double x=0,double y=0,double R=0);
    void setR(double,double,double);//半径
    double getR()
    {
        return R;
    }
    double areas();//圆面积
protected:
    double R;
};
Point::Point(double a,double b)
{
    x=a;
    y=b;
}
void Point::setPoint(double a,double b)
{
    x=a;
    y=b;
}
void Point::display()
{
    cout<<"( "<<getx()<<","<<gety()<<")"<<endl;
}
Circle::Circle(double a,double b,double r):Point(a,b),R(r) {}
void Circle::setR(double a,double b,double r)
{
    x=a;
    y=b;
    R=r;
}
double Circle::areas()
{
    return 3.14*R*R;
}
int main()
{
    Point p1(3,3),p2(8,8);
    Circle c(2,2,4);
    cout<<"第一点";
    p1.display();
    cout<<"第二点";
    p2.display();
    cout<<"原点为："<<"( "<<c.getx()<<","<<c.gety()<<")"<<" 半径为："<<c.getR()<<" 的圆的面积为："<<c.areas()<<endl;
    return 0;
}

感悟：大晚上的在宿舍编程序也不错啊！