Thread: Help checking compound angles question

Hi
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.

answer correct!

Originally Posted by mestmoha

answer correct!

I think I figured out why they differ. For it to be in the 3rd quadrant, I assume the angle has to be *less* than pi, else it will fall in the 1st or 2nd quadrant (as it is a negative angle, and we're working back from zero).

I'm starting to think the book is right