1.
\((1)\) 已知\(A\),\(B\),\(C\)是圆\(O\)上的三点,若\( \overrightarrow{AO}= \dfrac{1}{2}\left( \overrightarrow{AB}+ \overrightarrow{AC}\right) \),则\( \overrightarrow{AB} \)与\( \overrightarrow{AC} \)的夹角为_____.
\((2)\)不等式组\(\begin{cases}x+y\geqslant 1 \\ x-2y\leqslant 4\end{cases} \)的解集记为\(D.\)有下面四个命题:
\(①\):\(∀\left(x,y\right)∈D,x+2y⩾-2 \),\(②\):\(∃\left(x,y\right)∈D,x+2y⩾2 \),
\(③\):\(∀\left(x,y\right)∈D,x+2y⩽3 \), \(④\):\(∃\left(x,y\right)∈D,x+2y\leqslant -1 \).
其中真命题是_________
\((3)\) 已知椭圆\({C}_{1}: \dfrac{{x}^{2}}{{a}^{2}}+ \dfrac{{y}^{2}}{{b}^{2}}=1\left(a > b > 0\right) \)与双曲线\({C}_{1}:{x}^{2}- \dfrac{{y}^{2}}{4}=1 \)有公共的焦点,\({C}_{2} \)的一条渐近线与以\({C}_{1} \)的长轴为直径的圆相交于\(A\),\(B\)两点,若\({C}_{1} \)恰好将线段\(AB\)三等分,则短轴长为_________
\((4)\) 已知函数\(f\left( x \right)\)定义域为\(\left( 0,+\infty \right)\),其图象是连续不断的,且导数存在,若\(f\left( x \right) > x{f}{{{'}}}\left( x \right)\),则不等式\({{x}^{2}}f\left( \dfrac{1}{x} \right)-f\left( x \right) < 0\)的解集为________.