ACdream 1084 同心树

http://acdreamoj.sinaapp.com/problem.php?id=1084

证明过程  链接正方形的对角线   然后证明两个三角形相等；

#include<iostream>
#include<stdio.h>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;

int main( )
{
   int T;
   double N,a;
   scanf("%d",&T);
   while( T-- )
   {
       scanf("%lf%lf",&N,&a);
       if( a >= 90 ) a -= 90;
       if( a == 0 )
       {
           printf("%.2lf\n",N*N);
           continue;
       }
       a = a*3.141592654/180.0;
       double r = N/( 1 + cos(a) + sin(a) );
       printf("%.2lf\n",N*N-r*r*(sin(2*a)));
   }
   return 0;
}