What's the question, find f(x)?
I'm going to assume that is the case. Recall that:
cos(-x) = cos(x)
sin(-x) = -sin(x)
tan(-x) = -tan(x)
This is the same for their reciprocals. Knowing this, we reach here:
$\displaystyle -\frac{\cos{x}}{\sin{x}}\cdot \cos{x} - \sin{x}$
Combine sin(x) with the fraction to get:
$\displaystyle -\frac{\cos^2{x}}{\sin{x}} - \frac{\sin^2{x}}{\sin{x}}$
Can you continue now?