$\begin{aligned}
& \left|\begin{array}{ccc}
1+\sin ^2 x & \cos ^2 x & 4 \sin 4 x \
\sin ^2 x & 1+\cos ^2 x & 4 \sin 4 x \
\sin ^2 x & \cos ^2 x & 1+4 \sin 4 x
\end{array}\right|, x \in R \
& R_2 \rightarrow R_2-R_1 & R_3 \rightarrow R_3 \rightarrow R_1 \
& f(x)\left|\begin{array}{ccc}
1+\sin ^2 x & \cos ^2 x & 4 \sin 4 x \
-1 & 1 & 0 \
-1 & 0 & 1
\end{array}\right|
\end{aligned}Expandabout\mathrm{R}_1,usegetf(x)=2+4 \sin 4 x\therefore \mathrm{M}=maxvalueof\mathrm{f}(\mathrm{x})=6m=\minvalueoff(x)=-2\therefore \mathrm{m}^4-\mathrm{M}^4=1280$