$$\frac{1}{2} - \frac{1}{x^{2} + 1}$$
2*x
---------
2
/ 2\
\1 + x /
$$\frac{2 x}{\left(x^{2} + 1\right)^{2}}$$
/ 2 \
| 4*x |
2*|1 - ------|
| 2|
\ 1 + x /
--------------
2
/ 2\
\1 + x /
$$\frac{2 \left(- \frac{4 x^{2}}{x^{2} + 1} + 1\right)}{\left(x^{2} + 1\right)^{2}}$$