1.3-09:与圆相关的计算

#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
	double r;
	double pi=3.14159;
	cin>>r;
	double d=2*r;
	double c=2*pi*r;
	double s=pi*r*r;
	cout<<fixed<<setprecision(4)<<d<<" "<<c<<" "<<s;
	return 0;
}