Approximization of pi in c++

The value of can be determined by the series equation
=4 * ( 1 1/3+1/5 1/ 7+1 /9 1/ 11+1/13+... )
Write a recursive function that takes an odd number n and uses recursion to
approximate the value of using the given formula including term up through 1/n.
Your function prototype must be as follows:
float PiValue(int n);
Calling this function PiValue(1875) should give the answer 3.14052655581

i am really stuck in this program . Can anyone help me?

#include<cmath>
#include<iostream>
using namespace std;
float pic(int n)
{

float pi=4*(pow(1,n)*(1/(2*n-1)));

if(n==1)
{
    return pi;
}

    else
    {

    return pi+pic(n-1);
}
}
int main()
{
    int num;
   cout<<"Enter the odd number  "<<endl;    
   cin>>num;
   int r=pic(num);
   cout<<r<<endl;


   return 0;
}