Answer
(a) $\frac{8\pi}{3}$
$-\frac{4\pi}{3}$
(b) $\frac{23\pi}{12}$
$-\frac{25\pi}{12}$
Work Step by Step
(a) $\frac{2\pi}{3}+2\pi=\frac{2\pi}{3}+\frac{6\pi}{3}=\frac{8\pi}{3}$
$\frac{2\pi}{3}-2\pi=\frac{2\pi}{3}-\frac{6\pi}{3}=-\frac{4\pi}{3}$
(b) $-\frac{\pi}{12}+2\pi=-\frac{\pi}{12}+\frac{24\pi}{12}=\frac{23\pi}{12}$
$-\frac{\pi}{12}-2\pi=-\frac{\pi}{12}-\frac{24\pi}{12}=-\frac{25\pi}{12}$
