atan(x) ------- 2 x + 1
atan(x)/(x^2 + 1)
1 2*x*atan(x) ----------------- - ----------- / 2\ / 2 \ 2 \1 + x /*\x + 1/ / 2 \ \x + 1/
// 2 \ \ || 4*x | 3*x | 2*||-1 + ------|*atan(x) - ------| || 2| 2| \\ 1 + x / 1 + x / ---------------------------------- 2 / 2\ \1 + x /
/ 2 / 2 \ \ | 11*x | 2*x | | 4*|-2 + ------ - 6*x*|-1 + ------|*atan(x)| | 2 | 2| | \ 1 + x \ 1 + x / / ------------------------------------------- 3 / 2\ \1 + x /