Answer
$\sin 2x=2\sin x$
is not an identity.
Work Step by Step
$\displaystyle \sin(2\cdot 30^{o})=\sin(60^{o})=\frac{\sqrt{3}}{2}$
$2\displaystyle \sin(30^{o})=2\cdot\frac{1}{2}=1$
$\sin(2\cdot 30^{o})\neq 2\sin(30^{o})$
so
$\sin 2x=2\sin x$
is not an identity.
