For the sinusoidal function $\displaystyle {y}=-{6}{\cos{{\left[{4}{\left({x}-\frac{{\pi}}{{{2}}}\right)}\right]}}}$ determine each of the following:

amplitude = Preview Question 6 Part 1 of 3  

period = Preview Question 6 Part 2 of 3  

phase shift = Preview Question 6 Part 3 of 3  

Leave your answers in exact form; for example, type pi/6 for $\displaystyle \frac{{\pi}}{{{6}}}$ if necessary.