# Approximating a function using taylor series

I'm a little confused on how to go about approximating the function (Or part 2 of the 3 part question as shown in the image). Would I use the polynomial I got from part a but substitution a for x? Or would I use the formula $cos(0) - sin(0)(x-0) - \frac{cos(0)}{2!}(x-0)^2 + \frac{sin(0)}{3!}(x-0)^3 + \frac{cos(0)}{4!}(x-0)^4$? If I were to use the second formula, how would I go about simplifying the ratio using the formula? Any kind of guidance on this would be greatly appreciated.

Yes, it says to use $P_4(x)$ from (1) for (2). Simply put it into $$\frac{1-\cos(x)}{x}$$ for $\cos(x)$ and simplify.