Hi. I'm having problem writing this program as my assignment. I've spent hours on this but still i can't get the right answer.

Here is the question:
Write a C++ program to compute Sin(x) where

x x^3 x^5 x^7 x^9 x^n
sin (x) = ----- ─ ---- + ---- ─ ---- + ----- ─ . ------
1! 3! 5! 7! 9! n!

Your program should accept two values from the user (the angle x and the value of n) and then should compute and print the value of sin(x).

To make the program, do following tasks.

Write two functions, i.e. function to calculate factorial and function to calculate power having following prototypes.
double Factorial (int n); //Factorial function prototype
double Power(double x, int y); //Power function prototype
Use these functions in your main function to compute the series.

Till now, I've written the following program but I am not able to get the right answer.

#include <iostream>
using namespace std;

double fact (int f); //declaration of factorial function

double power(double x, int y); //declaration of power function


int main()
{
int x=0; //value of x in the series
float sum_pos = 0;
float sum_neg=0;
float t_sum=0;

cout << "Enter the value of x: " << endl;
cin >> x;

for (int i=1; i<=1000; i+=4)
{
sum_pos = sum_pos + (power (x,i) / fact (i));
}

for (int i=3; i<=1000; i+=4)
{
sum_neg = sum_neg + (power (x,i) / fact (i));
}

t_sum = sum_pos - sum_neg;

cout << "Sin of " << x << " = " << t_sum << endl;

return 0;
}

//Function for Factorial
double fact (int x)
{
double f=1;

if (x==0)
{
return f;
}

else
for (int i=1; i<=x; i++)
{
f=f*i;
}

return f;
}

//Function for Power
double power (double x, int y)
{
int p=1;

for (int i=1; i<=y; i++)
p=p*x;

return p;
}

I have to submit it this weekend. So please help me what am i doing wrong??