The following is an equation which I thought I had solved but my answer is different from that provided by my book, so I must have made a mistake. The problem is, I can't see where.
Solve the equation
One of my big difficulties with this kind of question is knowing which identity to use.
For example, in this question, saying
or
or
[
After looking at these three possibilities, I decided the second may be the best as everything is in terms of cos theta and it's quadratic...
And factorizing this:
So
But this is not what the books says the answer should be (
I would really appreciate it if anyone could tell me what's going wrong here because these trig identities are really giving me a hard time..!