#include
  
   
#include
   
     #include
    
      using namespace std; int A,B,y; double ans=0; double inline f(double x) { return A*x*x-(B*sin(x)+y); } double inline absf(double x) { if(f(x)<0)return -f(x); return f(x); } bool findans(double l,double r) //求绝对值后函数必然先减后增。三分 { if(f(l)*f(r)>0)return 0; while(r-l>0.00000001) //注意精度 { double mid1=l+(r-l)/3,mid2=r-(r-l)/3; if(absf(mid1)<=absf(mid2)) r=mid2; else l=mid1; } ans=l; return 1; } int main() { int T; scanf("%d",&T); while(T--) { scanf("%d%d%d",&A,&B,&y); bool marks=0;ans=0; for(double x=0;x<50;x=x+0.3) { if(findans(x,x+0.3)) { marks=1;break; } } if(marks) printf("%.5lf\n",ans); else printf("error\n"); } return 0; }