网上解释很详细
/* ***********************************************
Author :angon
************************************************ */
#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <stack>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
using namespace std;
#define showtime fprintf(stderr,"time = %.15f\n",clock() / (double)CLOCKS_PER_SEC)
#define lld %I64d
#define REP(i,k,n) for(int i=k;i<n;i++)
#define REPP(i,k,n) for(int i=k;i<=n;i++)
#define scan(d) scanf("%d",&d)
#define scanl(d) scanf("%I64d",&d)
#define scann(n,m) scanf("%d%d",&n,&m)
#define scannl(n,m) scanf("%I64d%I64d",&n,&m)
#define mst(a,k) memset(a,k,sizeof(a))
#define LL long long
#define N 1005
#define mod 1000000007
inline int read(){int s=0;char ch=getchar();for(; ch<'0'||ch>'9'; ch=getchar());for(; ch>='0'&&ch<='9'; ch=getchar())s=s*10+ch-'0';return s;}
const double PI = acos(-1);
int main()
{
//freopen("in.txt","r",stdin);
//freopen("out.txt","w",stdout);
int t;
double a;
//printf("%lf\n",2*sqrt(5));
scan(t);
while(t--)
{
scanf("%lf",&a);
a=a/2;
double A = acos(3.0/4);
double B = acos(5.0*sqrt(2)/8.0);
double C = 45.0/180.0*PI;
double s1 = 0.5*(a+2*a)*a - 0.5*2*a*a*sin(A) - (C- B)/2*4*a*a - (A + B - C)/2*a*a;
double s = (4-PI)*a*a - (4-PI)/4*a*a - 2*s1;
printf("%.2lf\n",s*2);
}
return 0;
}