I've been using this to compute the first order derivative's value of a function $f$ in a given point: f'(x) = \frac{f(x+\epsilon) - f(x-\epsilon)}{2\epsilon}
For some $\epsilon = 0.0001$ or so. But when I try to use the same formula for higher order derivatives it gives odd results
f''(x) = \frac{f'(x+\epsilon) - f'(x-\epsilon)}{2\epsilon} f''(x) = \frac{\frac{f(x+\epsilon+\epsilon) - f(x-\epsilon+\epsilon)}{2\epsilon} - \frac{f(x+\epsilon-\epsilon) - f(x-\epsilon-\epsilon)}{2\epsilon}}{2\epsilon}
What am I doing wrong here?