9.
\((1)\)若圆\(x\)\({\,\!}^{2}+\)\(y\)\({\,\!}^{2}-2\)\(x\)\(-4\)\(y\)\(=0\)的圆心到直线\(x\)\(-\)\(y\)\(+\)\(a\)\(=0\)的距离为\( \dfrac{ \sqrt{2}}{2}\),则\(a\)的值为________.
\((2)\)已知等比数列\(\{a_{n}\}\)满足\(a_{1}=3\),且\(4a_{1}\),\(2a_{2}\),\(a_{3}\)成等差数列,则此数列的公比等于________
\((3)\)向量\(a=(\)入\(.2)\),\(b=(-3.5)\),且\(a\)与\(b\)的夹角是锐角,则入得取值范围是________
\((4)\)给出以下结论:
\(①\)直线\({l}_{1},{l}_{2} \)的倾斜角分别为\({a}_{1},{a}_{2} \),若\({{l}_{1}}\bot {{l}_{2}}\),则\(|{{\alpha }_{1}}-{{\alpha }_{2}}|={{90}^{\circ }}\);
\(②\)对任意角\(\theta \),向量\({{e}_{1}}=(\cos θ,\sin θ) \)与\({e}_{2}=\left(\cos θ- \sqrt{3}\sin θ, \sqrt{3}\cos θ+\sin θ\right) \)的夹角都为\(\dfrac{\pi }{3}\);
\(③\)若\(\Delta ABC\)满足\(\dfrac{a}{\cos B}=\dfrac{b}{\cos A}\),则\(\Delta ABC\)一定是等腰三角形;
\(④\)对任意的正数\(a,b \),都有\(1 < \dfrac{\sqrt{a}+\sqrt{b}}{\sqrt{a+b}}\leqslant \sqrt{2}\).
其中所有正确结论的编号是_____________.