Inclined plane landing angle

If I have an smooth inclined plane of angle $\alpha$ to the horizontal, and a smooth particle sitting at the bottom of the slope. I give the particle an impulse up the slope at angle $\theta$ to the horizontal. Show that the landing angle is $\tan \phi=\frac {1}{\cot \theta-2\tan \alpha}$.

I know that $\tan \phi=-v_y/v_x$, and I have the values them in the textbook as standard results. I can't seem to simplify that though...