第一章课后题3_3（P58）

#include <iostream>
using namespace std;

const double pi = 3.14159;
int main()
{
double r;
cout << "输入r:";
cin >> r;
double l = 2.0*pi*r;
double s = pi*r*r;
cout << "\n周长是：" << l << endl;
cout << "面积是：" << s << endl;
system("pause");
return 1;
}