Answer
$\left( \frac{\sqrt{3}}{2}\right)^{-1/2}$
Work Step by Step
We have
$$
\lim _{y \rightarrow 3} \left(\sin\frac{\pi}{y}\right)^{-1/2}= \left(\sin\frac{\pi}{3}\right)^{-1/2}=\left( \frac{\sqrt{3}}{2}\right)^{-1/2}.
$$
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