Calculating sin(x) with the power series

[thropedo7]

Write a program that calculates the value of sin(x) from the power series x - (x^3/3!) + (x^5/5!) - (x^7/7!) + ..... The user should be prompted for both the value of x and the number of terms to include in the calculation.

My code seems to work for most numbers but if I input n (number of terms) greater than 7, then it just goes to a really high number. Also, how would I change my code so that the numbers are exact, not integers. Any help would be greatly appreciated!

#include <iostream>
#include <cmath>

using namespace std;

int PowerSeries(int x,int n)
{
int y=0;
int i=1;
int fSum=0;
int fFactorial=-1;

while (i<=n*2)
{
for (y=1;y<=i;y=y+1)
{
fFactorial=-fFactorial*y;
}
fSum=fSum+pow(x,i)/fFactorial;
i=i+2;
}

return fSum;
}

int main(void)
{
int n=0;
int x=0;

cout << " Please enter the value of x. " << endl;
cin >> x;

cout << " Please enter the number of terms. " << endl;
cin >> n;

cout << PowerSeries(x,n) << endl;
return 1;
}