pi / x \ -- - atan|-----| 4 \x + 2/
pi/4 - atan(x/(x + 2))
/ x \ pi - 4*atan|-----| \2 + x/ ------------------ 4
(pi - 4*atan(x/(2 + x)))/4
/ x \ pi - 4*atan|-----| \x + 2/ ------------------ 4
(pi - 4*atan(x/(x + 2)))/4
0.785398163397448 - atan(x/(x + 2))