My question is about the rules of proving trig identities rather than showing that both sides are equal to each other.
For example for a problem like this:
$(sin(x) + cos(x))^2 = 1 + sin (2x)$
From what I've been told, you start with one side and by only using that one side you must obtain the other side. And this is how these problems are done.
So do you have to do this for both sides for it to be a proof?
Are you allowed to move terms from the RHS to the LHS and vice versa?
Again, I'm not asking how to do the problem as I already know this, but I want to know the rules involved when proving a trig identity problem.