6*atan(3*x)
-----------
2
1 + 9*x
18*(1 - 6*x*atan(3*x))
----------------------
2
/ 2\
\1 + 9*x /
/ 2 \
| 9*x 36*x *atan(3*x)|
108*|-atan(3*x) - -------- + ---------------|
| 2 2 |
\ 1 + 9*x 1 + 9*x /
---------------------------------------------
2
/ 2\
\1 + 9*x /