From the following figure, which of the following is equal to $\tan (\theta/2)$?

$y = \sin \theta$
 

$\begin{align}
\tan (\theta/2) & = \dfrac{y}{1 + x} \\
\\
& = \dfrac{\sin \theta}{1 + \cos \theta}
\end{align}$
 

$\begin{align}
\tan (\theta/2) & = \dfrac{1 - x}{y} \\
\\
& = \dfrac{1 - \cos \theta}{\sin \theta}
\end{align}$