声明一个circle类

#include<iostream>
using namespace std;
class circle
{
double radius;
double area;
public:
void radius_input()
{
cout<<"请输入圆的半径:";
cin>>radius;
}
void c_area_out()
{
area=3.14*radius*radius;
cout<<"该圆的面积是:"<<area<<endl;
}
};
int main()
{
circle c1;
c1. radius_input();
c1.c_area_out();
return 0;
}