#define PI 3.14
#include
using namespace std;
int main()
{
double r,p,area;
cout<<"请输入半径";
cin>>r;
p=PI*r*2;
cout<<"周长:"<area=PI*r*r;
cout<<"面积:"< return 0;
}
#include }
using namespace std;
#define PI 3.1415927
void main()
{ double r,p,area;
cin>>r;
p=2*PI*r;
area=PI*r*r;
cout<