Answer
(a) $-\frac{\pi}{4}$
$\frac{7\pi}{4}$
(b) $\frac{28\pi}{15}$
$-\frac{32\pi}{15}$
Work Step by Step
(a) $-\frac{9\pi}{4}+2\pi=-\frac{9\pi}{4}+\frac{8\pi}{4}=-\frac{\pi}{4}$
$-\frac{\pi}{4}+2\pi=-\frac{9\pi}{4}+2(2\pi)=-\frac{9\pi}{4}+\frac{16\pi}{4}=\frac{7\pi}{4}$
(b) $-\frac{2\pi}{15}+2\pi=-\frac{2\pi}{15}+\frac{30\pi}{15}=\frac{28\pi}{15}$
$-\frac{2\pi}{15}-2\pi=-\frac{2\pi}{15}-\frac{30\pi}{15}=-\frac{32\pi}{15}$
