acot(4*x)
-4 --------- 2 1 + 16*x
128*x ------------ 2 / 2\ \1 + 16*x /
/ 2 \ | 64*x | 128*|1 - ---------| | 2| \ 1 + 16*x / ------------------- 2 / 2\ \1 + 16*x /