$\begin{aligned}
& \sin x+\sin ^2 x=1 \
& \Rightarrow \sin x=\cos ^2 x \Rightarrow \tan x=\cos x
\end{aligned}\thereforeGivenexpression\begin{aligned}
& =2 \cos ^{12} x+6\left[\cos ^{10} x+\cos ^8 x\right]+2 \cos ^6 x \
& =2\left[\sin ^6 x+3 \sin ^5 x+3 \sin ^4 x+\sin ^3 x\right] \
& =2 \sin ^3 x\left[(\sin x+1)^3\right] \
& =2\left[\sin ^2 x+\sin x\right]^3 \
& =2
\end{aligned}$