Limits Continuity And Differentiability

If $f(x)=\left\{\begin{array}{cc}\frac{x-[x]}{x-2}, & x > 2 \\ b, & x=2 \\ \frac{\left|x^2-x-2\right|}{a\left(2+x-x^2\right)}, & -1 < x \leq 2 \\ 2 a-b, & x \leq-1\end{array}\right.$

is continuous on $R$, then $\lim _{x \rightarrow 0} \frac{\sin ^2 a x+x \tan b x}{x^2}=$