float Cylinder::area()const
{
      return 2*Circle::area()+2*3.1415*r*height;
      
}      
          
float Cylinder::volume()const
{
     return Circle::area()*height; 
      
}       
 
void Cylinder::showname()const
{
     cout<<"the information of the cylinder: ";
     
} 

void Cylinder::display()const
{
     Circle::display();
     cout<<"the height="<<height<<endl;
}