I am having difficulties getting the critical values and interval values. There is a hint and I think I need to reduce the function to make it work better, before starting. What would be the reduced function?

Here is the question.

Including all steps, charts, and derivations details, use the curve sketching methods to sketch the graph of the given functionon the interval -2?

(*HINT : Make sure that you reduce your function and its derivative to more effectively find the second derivative. Before starting to derive, you can substitute with a trigonometric identity and reduce the function to the form : a + b/c where a and b are real numbers.)

cos (2x y = 3 - 2 sin