9.
已知\(α∈(0, \dfrac{π}{4}),β∈( \dfrac{π}{4}, \dfrac{π}{2}), \overrightarrow{a}=(2{\cos }^{2}α,2\sin α\cos α) \),\(\overrightarrow{b}=(1+\sin β\cos β,1-2{\sin }^{2}β), \overrightarrow{c}=(1,0)· < \overrightarrow{a}, \overrightarrow{c} > ={θ}_{1}, < \overrightarrow{b}, \overrightarrow{c} > ={θ}_{2} ..\)
\((1)\)若\({θ}_{2}= \dfrac{π}{6} \),求角\(β\);
\((2)\)若\({θ}_{2}-{θ}_{1}= \dfrac{π}{6} \),求\(\sin (β-α)\).