atan(2*x + 3)
2 -------------- 2 1 + (2*x + 3)
-8*(3 + 2*x) ----------------- 2 / 2\ \1 + (3 + 2*x) /
/ 2 \ | 4*(3 + 2*x) | 16*|-1 + --------------| | 2| \ 1 + (3 + 2*x) / ------------------------ 2 / 2\ \1 + (3 + 2*x) /