Answer
See below:
Work Step by Step
We are given $\theta =\frac{\pi }{3}$. Therefore,
$\begin{align}
& \tan \theta =\tan \frac{\pi }{3} \\
& \tan \theta =\sqrt{3}
\end{align}$
As $ x=r\cos \theta \ \text{ and }\ y=r\sin \theta $.
$\begin{align}
& \frac{r\sin \theta }{r\cos \theta \ }=\frac{y}{x} \\
& \tan \theta =\frac{y}{x}
\end{align}$
Also, $\tan \theta =\sqrt{3}$
Therefore,
$\begin{align}
& \frac{y}{x}=\sqrt{3} \\
& y=\sqrt{3}x
\end{align}$
Thus, the provided equation is the equation of line with slope $\sqrt{3}$.
