#### Answer

The Derivative is:
$y'=\sin x\sec^2 x+\sin x$

#### Work Step by Step

$f(x)=\sin x\tan x$
Using Product Rule to find the Derivative:
$y'=h'(x)\cdot g(x)+h(x)\cdot g'(x)$
$y'=(\cos x)(\tan x)+(\sin x)(\sec^2 x)$
$y'=\cos x \frac{\sin x}{\cos x}+\sin x\sec^2 x$
$y'=\sin x\sec^2 x+\sin x$