Hi I was wondering if someone could please help me out with this question:

Sketch the graph y = 4 cos (2x) for x : (0,5π/2]

When sketching circular functions, you should calculate the period and amplitude first.

In this case, the graph is only dilated from the x,y axis and isn't translated or reflected, therefore you can just imagine the basic shape of a cosine graph and then morph it into the correct graph by using the amplitude and period. After you've got the general shape, sub in the end points and mark in all the relevant coordinates.