Answer
The two values of $\theta $ are $\frac{\pi }{4}$ and $\frac{3\pi }{4}$.
Work Step by Step
We have the given expression: $\sin \theta =\frac{\sqrt{2}}{2}$.
Here, the reference angle is $\frac{\pi }{4}$ and $\theta $ lies in quadrants I or II.
Consider: the angle $\theta $ lies in quadrant I.
$\theta =\frac{\pi }{4}$
Consider: the angle $\theta $ lies in quadrant II.
$\begin{align}
& \theta =\pi -\frac{\pi }{4} \\
& =\frac{4\pi -\pi }{4} \\
& =\frac{3\pi }{4}
\end{align}$
