The answer is sin(x). So you have sin^2(-x)- sin(-x) / 1 - sin(-x) . sin^2(-x) is really just sin(-x) * sin(-x), which becomes -1*-1*sin(x)*sin(x) = sin^2 (x). So you have sin^2 (x) - sin(x) / sin(x) + 1. Take out the sin(x) on the top and you have

(sin(x)( sin(x) + 1)) / (sin(x) + 1). Cancel out the (sin(x)+1) and you have sin(x) left.