已知函数\(f(x)=2\sin (ωx+φ)(ω > 0,- \dfrac {π}{2} < φ < \dfrac {π}{2})\)的部分图象如图所示,直线\(x= \dfrac {π}{12}\),\(x= \dfrac {7π}{12}\)是其相邻的两条对称轴.
\((1)\)求函数\(f(x)\)的解析式;
\((2)\)若\(f( \dfrac {α}{2})=- \dfrac {6}{5}\),且\( \dfrac {2π}{3} < α < \dfrac {7π}{6}\),求\(\cos α\)的值.