如图，角\(α\)的始边与\(x\)轴的非负半轴重合，终边与单位圆交于点\(A\) \((x_{1},y_{l})\)，将射线\(OA\)按逆时针方向旋转\( \dfrac {2π}{3}\)后与单位圆交于点\(B(x_{2},y_{2})\)，\(f(a)=x_{l}-x_{2}\)．
\((\)Ⅰ\()\)若角\(α\)为锐角，求\(f(α)\)的取值范围；
\((\)Ⅱ\()\)比较\(f(2)\)与\(f(3)\)的大小．