atan(2*x - 1)
d --(atan(2*x - 1)) dx
2
--------------
2
1 + (2*x - 1)
-8*(-1 + 2*x)
------------------
2
/ 2\
\1 + (-1 + 2*x) /
/ 2 \
| 4*(-1 + 2*x) |
16*|-1 + ---------------|
| 2|
\ 1 + (-1 + 2*x) /
-------------------------
2
/ 2\
\1 + (-1 + 2*x) /