Can someone explain how $\frac{\tan x}{\sec x}=\sin x$? What identities are used to get $\sin x$ from $\tan x \operatorname{/} \sec x$? I was looking at an example in my textbook and the problem went from $\tan x \operatorname{/} \sec x$ to $\sin x$. I don't understand how.
Hints:


  $\tan x=\frac{\sin x}{\cos x}$ and $\sec x=\frac{1}{\cos x}$
$\tan(\pi/2) = \infty$ and $\sec(\pi/2)$ is undefined whereas $\sin(\pi/2) = 1$ so the given equation is incorrect.