9.
设向量\( \overrightarrow{a}=(\sin x, \sqrt {3}\cos x), \overrightarrow{b}=(-1,1), \overrightarrow{c}=(1,1).(\)其中\(x∈[0,π])\)
\((1)\)若\(( \overrightarrow{a}+ \overrightarrow{b})/\!/ \overrightarrow{c}\),求实数\(x\)的值;
\((2)\)若\( \overrightarrow{a}\cdot \overrightarrow{b}= \dfrac {1}{2}\),求函数\(\sin (x+ \dfrac {π}{6})\)的值.