Question 1035649
At t=0, the function is d=5 cos (0)=5
The maximum displacement is the cosine coefficient or 5.
For one oscillation, the period, it is 2pi/(pi/3)=6
For the equilibrium position, it is one-quarter of the period, or 1.5 pi/3
and 4.5 pi/3.  The cosine is 1 at 0, 0 at pi/2 and again at 3pi/2