So I started working on my for my Exam and I wanted to know if I get this graph right!

So a graph is given to me

<<< this is the graph

So I looked for the amplitude and the period..
and I think that the amplitude is
[A]= 2-(-2)=4/2= 2, so amplitude is 2

Then the period I am not really sure.... I have 2pi/4= pi/2, so I assume that the period is pi/2

Now The example ask me to Find an equation for sine function for the graph

So I conclude that is y=-2sin(pi/2x-pi/2) since it looks like an inverse curve for sine.

and Now it ask me a cosine function

So I conclude that is y= 2cos(pi/2x-pi/2)

No, the period is not \displaystyle \begin{align*} \frac{\pi}{2} \end{align*}. Choose a starting point on your graph, e.g. x = 0. How far do you move along the x axis until the graph repeats itself?