
$\begin{aligned}
& \mathrm{mg} \sin 45=\mathrm{f}{\mathrm{L}} \
& \mathrm{mg} \cos 45=\mathrm{N} \
& \mathrm{f}{\mathrm{L}}=\mu_{\mathrm{s}} N \
& \mu_{\mathrm{s}}=\tan 45=1
\end{aligned}or\tan \theta=\mu_s(\thetaisangleofrepose)\tan 45=\mu_{\mathrm{s}}=1$