Visual C++ :: Creating Program To Make Sine Function Without Any Library Other Than Iostream?

My assignment is to create a C++ Program to find the sine of a number without any library other than iostream by using Taylor Series:

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

Here is what i have done till now:

#include <iostream>
double fact (int f); //declaration of factorial function
double power(double x, int y); //declaration of power function
double sin(int x); //declaration of sine function
//double cos(int x); //declaration of cosine function
//double tan(int x); //declaration of tangent function

[code]....