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

a. -sin x
b. sin x
c. -csc x
d. csc x

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:
is the same as
We can now cancel out the cos(x), which leaves us only with -sin(x) remaining. So your answer is A.