Let a sin b b pi find in terms of b the solutions of sin x

So far I just tried to do the obvious and substitute -a for - sin b. Like so; sin 2x = - sin b which then becomes; sin 2x = sin -b and then I can remove the sines and rearrange for x, which gives me this. 2x = -b x = -b/2 However, if I were to look at the domain of b. Any value within the domain will give a value that doesn't fit the domain of x. Any suggestions would be great. Thank you!