nyoj 1234 签到题,一个很简单的数学题;

签到题 nyoj 1234 ,题目链接 click here

签到题
时间限制：1000 ms | 内存限制：65535 KB
难度：2
描述
hrw最近看到一个有趣的几何题，题目描述是这样的：一个大圆盘里面放入许多小圆盘，每个小圆盘必须接触大圆盘边缘且与其他小圆盘不能相交，但它们可以互相接触，每个小圆盘具有相同的半径，求此条件下能否放入n个小圆盘。

输入
Multiple sets of test data，The first line contains three integers n, R and r (1 ≤ n ≤ 100, 1 ≤ r, R ≤ 1000) — the number of plates, the radius of the table and the plates’ radius.and you can think the pi is 3.1415927
输出
Print “YES” (without the quotes) if it is possible to place n plates on the table by the rules given above. If it is impossible, print “NO”.Remember, that each plate must touch the edge of the table.
样例输入
4 10 4
2 10 10
样例输出
YES
NO

#include
#include
int main()
{
    int R,r,n;
    double pi = 3.141592653 ;
    while(~scanf("%d%d%d",&n,&R,&r))
    {
        if(n==1&&r<=R)
        {
            printf("YES\n");
            continue;
        }
        double x=1.0*r/(R-r);
        double a = asin(x)*180.0/pi;
        a=a*2.0*n-0.0000001;//精度问题;
        if(a<=360.00000000000)
            printf("YES\n");
        else
            printf("NO\n");
    }
    return 0;
}