## Trigonometry (11th Edition) Clone

$$-\tan x\cos x=\sin(-x)$$ $\text{C}$ is the answer.
$$A=-\tan x\cos x$$ A Quotient Identity related to $\tan x$ states that $$\tan\theta=\frac{\sin\theta}{\cos\theta}$$ That means we can rewrite $A$ as follows: $$A=-\frac{\sin x}{\cos x}\cos x$$ $$A=-\sin x$$ Also, from Negative-Angle Identities, we know $$\sin(-\theta)=-\sin\theta$$ Therefore, $$A=\sin(-x)$$ $\text{C}$ is the answer.