using?namespace?std;
class?point{
public:
point(?double?x?=?0.0,?double?y?=?0.0?){
m_x?=?x;
m_y?=?y;
}
void?show(){
cout?<<?"x?=?"?<<?m_x?<<?","?<<?"y?=?"?<<?m_y?<<?endl;
}
private:
double?m_x;
double?m_y;
};
class?circle?:?public?point{
public:
circle(?double?r,?double?x?=?0.0,?double?y?=?0.0)
:?point(?x,?y){
m_r?=?r;
}
void?show(){
point::show();
cout?<<?"r?=?"?<<?m_r?<<?endl;
}
private:
double?m_r;
};
int?main()
{
circle?dc(100,20,30);
dc.show();
return?0;
}