Question

Which expression is equivalent to (cos x)(tan(-x))?
a) -sin x
b) sin x
c) -csc x
d) csc x

Answer 1

Firstly :
\[\tan(-x) = -\tan(x)\]

Answer 2

Secondly:
\[\tan(x) = \frac{\sin(x)}{\cos(x)}\]

Replace tan(x) with the above Identity, cancel out whatever is being cancelled and you have your answer with you then. :)