If anyone can show me how to complete this I would be thankful.
$\displaystyle \tan x = 2 \sin x \Rightarrow \frac{\sin x}{\cos x} = 2 \sin x \Rightarrow \sin x = 2 \sin x \cos x \Rightarrow \sin x \, (1 - 2 \cos x) = 0$.
$\displaystyle \tan x = 2 \sin x
\Rightarrow \frac{\sin x}{\cos x} = 2 \sin x \Rightarrow \sin x = 2 \sin x \cos x \Rightarrow \sin x \, (1 - 2 \cos x) = 0$