atan(cos(x))
-sin(x) ----------- 2 1 + cos (x)
/ 2 \ | 2*sin (x) | -|1 + -----------|*cos(x) | 2 | \ 1 + cos (x)/ -------------------------- 2 1 + cos (x)
/ 2 2 2 2 \ | 6*cos (x) 2*sin (x) 8*cos (x)*sin (x)| |1 - ----------- + ----------- - -----------------|*sin(x) | 2 2 2 | | 1 + cos (x) 1 + cos (x) / 2 \ | \ \1 + cos (x)/ / ---------------------------------------------------------- 2 1 + cos (x)