Hello, I have found this to be a very helpful place, so I'm going to ask another question
Find the amplitude, period, a phase shift and the mean of the following function.
$\displaystyle y=3cos(x/3-pi/6)+5$
$\displaystyle y = A\cos\left[B\left(x + C\right)\right] + D$
$\displaystyle |A|$ = amplitude
$\displaystyle \frac{2\pi}{|B|}$ = period
$\displaystyle C$ = phase shift
$\displaystyle D$ = vertical shift = mean
now, relate all of the above to your specific function ...
$\displaystyle y = 3\cos\left[\frac{1}{3}\left(x - \frac{\pi}{2}\right)\right] + 5$