HDU-5858 Hard problem（计算几何）

题目：https://vjudge.net/problem/469269/origin
题意：求阴影面积
思路：三角函数

代码：
见http://blog.csdn.net/pnan222/article/details/52275172

（图画出来也就出来
了

#include<bits/stdc++.h>using namespace std;int main(){    int T;    double L;    cin>>T;    while(T--)    {        scanf("%lf",&L);        double A = acos(5.0*sqrt(2) / 8.0);        double B = asin(2.0 * sin(A));        //cout<<A<<endl<<B<<endl;        double S1 = 1/2.0 * 2.0 * A *L*L;        double S2 = 1/2.0 * 2.0 * B *(L/2)*(L/2);        //cout<<S1<<endl<<S2<<endl;        //计算三角形的面积        double a = L,b = L/2,c = L*sqrt(2.0)/2;        double p = (a+b+c)/2.0;        double S3 = sqrt(p*(p-a)*(p-b)*(p-c));        //cout<<S3<<endl;        double S = S2+2*S3-S1;        printf("%.2f\n",S*2);    }}