> #include<iostream>
> #include<stdio.h>
> #include<cmath>
> using namespace std;
> int main()
> {
> 	int n,i,test;
> 	double R;
>     cin>>test;
> 	for(i=1;i<=test;i++)
> 	{
> 	   cin>>R>>n;
> 	   printf("Scenario #%d:\n%.3f\n\n",i,R*sin(acos(-1)/n)/(1+sin(acos(-1)/n)));
> 	}
> 	return 0;
> }
> 应该是这样的!!!!!!!!!!