2.
\((1)\)设函数\(f(x)=\begin{cases} & x+1,x\leqslant 0, \\ & {{2}^{x}},x > 0, \\ \end{cases}\)且,则\(f(f(-\dfrac{1}{2}))=\) .
\((2)\)设扇形的半径长为\(2cm\),面积为\(4c{{m}^{2}}\),则扇形圆心角的弧度数是 \((\)圆心角为正角\()\).
\((3)\overrightarrow{a}\),\(\overrightarrow{b}\)的夹角为\(120^{\circ}\),\(|\overrightarrow{a} |=1\),\(|\overrightarrow{b} |=3\),则\(|5\overrightarrow{a}-\overrightarrow{b} |=\)________.
\((4)\)已知\(f\left( x \right)={{x}^{3}}+\left( a-1 \right){{x}^{2}}\)是奇函数,则不等式\(f\left( ax \right) > f\left( a-x \right)\)的解集是 .