acot(x) ------- - acot(x) 2
acot(x)/2 - acot(x)
1 ---------- / 2\ 2*\1 + x /
-x --------- 2 / 2\ \1 + x /
2 4*x -1 + ------ 2 1 + x ----------- 2 / 2\ \1 + x /