now multiply both sides by sin(x) and divide both sides by 2
and has said what to do next. Well, this gives:
In answer to your question 'do I square both sides' - no. You should take the square root now, to get on the LHS. But can you see what the problem is with trying to take the square root of the RHS?
As it stands, then, this equation has no real solutions. Perhaps you should check that you copied it down correctly.