I have a mental block on a certain very simple trigonometry problem. I know I will slap my forehead when I see the solution. I therefore ask for your indulgence and thank, in advance, any responders. Here is the question and my attempt:
Using , show that the equation can be written as provided that .
Here is what I have done already:
I am not at all sure that I am on the right track. Any help would be sincerely appreciated.