Answer
(a) amplitude $\frac{1}{10}$, period $\pi$, horizontal shift $-\frac{3\pi}{4}$
(b) $y=-\frac{1}{10}cos2(x+\frac{3\pi}{4})$,
Work Step by Step
(a) Based on the standard forms given $y=a\cdot sink(x-b)$ or $y=a\cdot cosk(x-b)$,
we can find the amplitude of the function as $|a|=\frac{1}{10}$, the period as $\pi$, and horizontal shift as $b=-\frac{3\pi}{4}$
(b) Since period=$\frac{2\pi}{k}=\pi$, we have $k=2$, and the equation for this case is $y=-\frac{1}{10}cos2(x+\frac{3\pi}{4})$,