Question 119
Find the range $E_{f}$ of the function $f: \mathbb{R} \setminus \{-1,0,1\} \rightarrow \mathbb{R}$,
$$
f(x)=\operatorname{arctg}\left(\frac{x}{x+1}\right)+\operatorname{arctg}\left(\frac{x}{x-1}\right)-\operatorname{arctg}\left(\frac{1}{2 x^{2}}\right)
$$
$$
f(x)=\operatorname{arctg}\left(\frac{x}{x+1}\right)+\operatorname{arctg}\left(\frac{x}{x-1}\right)-\operatorname{arctg}\left(\frac{1}{2 x^{2}}\right)
$$