LHL at x=2π x→2πlim(78)tan7xtan8x=(78)0=1
RHL at x=2π $\begin{aligned}
& \lim _{x \rightarrow \frac{\pi}{2}}(1+|\cot x|)^{\frac{b}{\operatorname{lan}} \tan x} \
& =e^{\lim _{x-\frac{\pi}{2}}|\cot x| \frac{b}{a}|\tan x|}=e^{\frac{b}{a}}
\end{aligned}\begin{aligned} & \Rightarrow 1=a-8=e^{\frac{b}{a}} \ & \Rightarrow a=9, b=0 \ & \Rightarrow a^2+b^2=81\end{aligned}$