Question

http://prnt.sc/b6cuhy

Answer 1

Let's look at the amplitude and the period separately.
You need the function to have a maximum value of 9 and a minimum value of 1.

What is the maximum value of \(\cos \dfrac{\pi}{2} t\)?

Answer 2

Also, what is the minimum value of \(\cos \dfrac{\pi}{2} t\)?

Answer 3

Let's backup a bit.

In general, for the cosine function,
what are the maximum and minimum values of \(\cos \theta\) ?

Answer 4

i don't really know,,