Question

Which expression is equivalent to (cos x)(tan(–x))?

Answer 1

The tan(-x) is the same thing as -tan(x).  The tangent function is also the same thing as sin(x)/cos(x), right? So let's rewrite that tan in terms of sin and cos:
$[cos(x)][tan(-x)]$ is the same as $[cos(x)][ -\frac{sin(x)}{cos(x)}]$
We can now cancel out the cos(x), which leaves us only with -sin(x) remaining. So your answer is A.

Answer 2

The answer to this is A