10.
已知\( \overrightarrow{m}=(2\cos x,y-2 \sqrt {3}\sin x\cos x)\),\( \overrightarrow{n}=(1,\cos x)\),且\( \overrightarrow{m}/\!/ \overrightarrow{n}\).
\((\)Ⅰ\()\)试将\(y\)表示为\(x\)的函数\(f(x)\),并求\(f(x)\)的单调递增区间;
\((\)Ⅱ\()\)已知\(a\)、\(b\)、\(c\)分别为\(\triangle ABC\)的三个内角\(A\)、\(B\)、\(C\)对应的边长,若\(f( \dfrac {C}{2})=3\),且\(c=2 \sqrt {6}\),\(a+b=6\),求\(\triangle ABC\)的面积.