C++ partial Sum

#include <vector>
#include <iostream>
using namespace std;

double sum(int n)
{
double partialSum = 0.0;
for (int k = 2; k <= n; k++)
{
partialSum += sqrt(k / (k + 1.)) -sqrt((k - 1.) / k);
}
return partialSum;
}
int main(int argc,char*argv)
{
cout << sum(1000) << endl;
return 0;
}