Answer
$$\tan x=\frac{\sin x}{\cos x}$$
$\text{D}$ is the answer here.
Work Step by Step
$$\tan x$$
According to the Quotient Identities, we have
$$\tan\theta=\frac{\sin\theta}{\cos\theta}$$
Therefore, $$\tan x=\frac{\sin x}{\cos x}$$
which means we would pick $\text{D}$ as the answer here.