No, that is not the only solution, though it is certainly one solution. Not the most general answer, though. When do two sine functions equal each other? What is true of the arguments of the sine functions?
Well, I hate to be tough on you, but I think it's the best thing for you. I feel that I've given you enough hints to finish the problem. What's left really isn't all that earth-shattering. Just look over the hints, maybe collect everything in one place, compare equations, and see if something doesn't come to mind.