9.
已知圆\(O\):\(x^{2}+y^{2}=1\)与\(x\)轴负半轴相交于点\(A\),与\(y\)轴正半轴相交于点\(B\)
\((1)\)若过点\(C( \dfrac {1}{2}, \dfrac { \sqrt {3}}{2})\)的直线\(l\)被圆\(O\)截得的弦长为\( \sqrt {3}\),求直线\(l\)的方程;
\((2)\)若在以\(B\)为圆心半径为\(r\)的圆上存在点\(P\),使得\(PA= \sqrt {2}PO(O\)为坐标原点\()\),求\(r\)的取值范围;
\((3)\)设\(M(x_{1},y_{1})\),\(Q(x_{2},y_{2})\)是圆\(O\)上的两个动点,点\(M\)关于原点的对称点为\(M_{1}\),点\(M\)关于\(x\)轴的对称点为\(M_{2}\),如果直线\(QM_{1}\)、\(QM_{2}\)与\(y\)轴分别交于\((0,m)\)和\((0,n)\),问\(m⋅n\)是否为定值?若是求出该定值;若不是,请说明理由.