Forgive me if this is the incorrect forum - I consider compound angles to be trig, but maybe they're not!
I'm struggling to obtain the same answer as that given in a textbook. I'll give you my answer - I'd appreciate any help where I might have gone wrong:
Convert to the form
I make this
Is this in the 3rd quadrant as I think it is? The answer the book gives seems to imply the answer is in the second quadrant.