$\frac{\pi}{12}$

$\frac{\pi}{8}$

$\frac{5 \pi}{12}$

$\frac{5 \pi}{8}$

$n$ A=3

$n+\frac{1}{A}=-\frac{1}{2}$

$A+n=1$

$A=n$

$\frac{1}{3} \log \left(\frac{x+1}{x^2+x+1}\right)+C$

$\frac{1}{3} \log \left(\frac{(x-1)^2}{x^2+x+1}\right)+C$

$\frac{1}{3} \log \left(\frac{x-1}{x^2+x+1}\right)+C$

$\frac{1}{3} \log \left(\frac{(x+1)^2}{x^2-x+1}\right)+C$

$\frac{x^2+8 x+C}{2}$

$x^2+8 x+C$

$x^3-4 x+C$

$\frac{x^2-8 x+C}{2}$