atan(x + 1)
d --(atan(x + 1)) dx
-2*(1 + x)
---------------
2
/ 2\
\1 + (1 + x) /
/ 2 \
| 4*(1 + x) |
2*|-1 + ------------|
| 2|
\ 1 + (1 + x) /
---------------------
2
/ 2\
\1 + (1 + x) /