303

a)
\frac{\pi}{2}{,}\frac{3\pi}{2}{,}\frac{5\pi}{2}{,}\frac{7\pi}{2}{,}\frac{9\pi}{2}
b)
\tan\frac{\pi}{4}-\tan\frac{3\pi}{4}+\tan\frac{11\pi}{12}=1-\left(-1\right)+\left(-\left(2+\sqrt{3}\right)\right)=2-2-\sqrt{3}=-\sqrt{3}