圆的计算

不需要太多头文件
(也可以直接用万能头 # include <bits/stdc++.h>
我这里就不用万能头了
（已缩进，可抄）

---

# include <iostream>
# include <cstdio>
using namespace std;
int main(){
    double pi = 3.14159;
    double r;
    cin>>r;
    double d = r+r;
    double C = pi*d;
    double S = r*r*pi;
    printf("%.4f",d);
    cout<<" ";
    printf("%.4f",C);
    cout<<" ";
    printf("%.4f",S);
    
    return 0;
}