9.
已知向量\(\overrightarrow{a}=\left( \sin \alpha ,-2 \right)\)与\(\overrightarrow{b}=\left( 1,\cos \alpha \right)\),其中\(\alpha \in \left( 0,\dfrac{\pi }{2} \right)\)。
\((1)\)问向量\(\overrightarrow{a},\overrightarrow{b}\)能平行吗?请说明理由;
\((2)\)若\(\overrightarrow{a}\bot \overrightarrow{b}\),求\(\sin \alpha \)和\(\cos \alpha \)的值;
\((3)\)在\((2)\)的条件下,若\(\cos \beta =\dfrac{\sqrt{10}}{10},\beta \in \left( 0,\dfrac{\pi }{2} \right)\),求\(\alpha +\beta \)的值。