trigonometry - How to solve arcsin(x1/x2 * sin(theta)

$$f = \arcsin\left(\frac {x_1}{x_2} * \sin(\theta)\right)$$

I think this is a simple question, but is there an easy way of solving this equation? Is there a way to solve without having to sin both sides of the equation? Is there some sort of trigonometric identity I can use for this issue?

Thanks!