poj 1905

#include<iostream>#include<math.h>#include<iomanip>#include<cstdio>using namespace std;#define eps 1e-6double L,h,s;int ok(double x)//一不小心就写成int了  精度达不到{    return 2*x*asin(L/(2*x)) < s;}int main(){    double n,c;    while(cin>>L>>n>>c)    {         if(L<0 && n<0 && c<0)            break;        double l=0.0,r=L*0.5;        double mid;        s=(1+n*c)*L;        while(r-l>1e-6)        {           mid=(l+r)/2;           r=(4*mid*mid+L*L)/(8*mid);           if(ok(r)) l=mid;           else           r=mid;        }        h=mid;        printf("%.3lf\n",h);    }    return 0;}