For $\displaystyle {y}=-{3}{\cos{{\left({x}-{\frac{{\pi}}{{{2}}}}\right)}}}$,
its amplitude is Preview Question 6 Part 1 of 3   ;
its period is Preview Question 6 Part 2 of 3   ;
Use radians and use pi for $\displaystyle \pi$.
its phase shift is Preview Question 6 Part 3 of 3   ;