HDU 5858 Hard problem

公式题。

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<iostream>
#include<ctime>
using namespace std;
typedef long long LL;
const double pi=acos(-1.0);
void File()
{
    freopen("D:\\in.txt","r",stdin);
    freopen("D:\\out.txt","w",stdout);
}

int main()
{
    double L; int T; scanf("%d",&T);
    while(T--)
    {
        scanf("%lf",&L);
        double s1=sqrt(7.0);
        double s2=asin(s1/4);
        double s3=4*asin(5.0*s1/16);

        double ans=L*L/4*(pi+s1-s2-s3);
        printf("%.2lf\n",ans);
    }
    return 0;
}