$$\frac{4 x}{x^{4} + 1}$$
/ 4 \
| 4*x |
4*|1 - ------|
| 4|
\ 1 + x /
--------------
4
1 + x $$\frac{1}{x^{4} + 1} \left(- \frac{16 x^{4}}{x^{4} + 1} + 4\right)$$
/ 4 \
3 | 8*x |
16*x *|-5 + ------|
| 4|
\ 1 + x /
-------------------
2
/ 4\
\1 + x / $$\frac{16 x^{3}}{\left(x^{4} + 1\right)^{2}} \left(\frac{8 x^{4}}{x^{4} + 1} - 5\right)$$