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；

 1 #include<iostream>
 2 #include<stdio.h>
 3 #include<cstring>
 4 #include<algorithm>
 5 #include<cmath>
 6 using namespace std;
 7 
 8 int main( )
 9 {
10    int T;
11    double N,a;
12    scanf("%d",&T);
13    while( T-- )
14    {
15        scanf("%lf%lf",&N,&a);
16        if( a >= 90 ) a -= 90;
17        if( a == 0 )
18        {
19            printf("%.2lf\n",N*N);
20            continue;
21        }
22        a = a*3.141592654/180.0;
23        double r = N/( 1 + cos(a) + sin(a) );
24        printf("%.2lf\n",N*N-r*r*(sin(2*a)));
25    }
26    return 0;
27 }