That doesn't make sense to me.
Are you sure it's not:
or
??
In any case, the range of a function, is the range of values of or that emerge as or vary across their domain.
Your function is a sine wave, hence or vary from and . or , a sine wave ranges between positive and negative its amplitude. Do you know what the amplitude of your sinewave is? Let the amplitude be .
Hence the range is
or
But what is a? That's the bit you have to do!
Depending on which was meant. Unless your equation is actually correct and there's an extra element to this question that I don't understand.