Here the answer:
#include<iostream>
#include<vector>
#include<cmath>

using namespace std;

int main(){
double x;
vector<double>a;
while(cin>>x)a.push_back(sqrt(x));

for(int i=a.size()-1;i>=0;i--)printf("%.4f\n",a[i]);
return 0;
}

Didn't "while(cin>>x)" lead to endless loop?

it may..
while(cin>>x==1)