At first, we sample $f(x)$ in the $N$ ($N$ is odd) equidistant points around $x^*$: [ f_k = f(x_k),: x_k = x^*+kh,: k=-frac{N-1}{2},dots,frac{N-1}{2} ] where $h$ is some step. Then we interpolate points ${(x_k,f_k)}$ by polynomial begin{equation} label{eq:poly}...