به ازای کدام مقدار $a$ تابع $f\left( x \right)=\left\{ \begin{matrix}
\frac{\left| x \right|\sin 2x}{{{x}^{2}}}\,\,\,\,\,\,\,\,;\,\,\,\,\,\,\,x\ne 0 \\
a-1\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,;\,\,\,\,\,\,\,x=0 \\
\end{matrix} \right.$ در $x=0$ از چپ پیوسته است؟