已知\(\overrightarrow{a}=(\sin x+\cos x,-2\sin x),\overrightarrow{b}=(\sin x-\cos x,\sqrt{3}\cos x)\)
\((1)\)若\(\overrightarrow{a}\cdot \overrightarrow{b}=2\),当\(x\in (0,\pi )\)时,求\(x\)的值
\((2)\)设\(f(x)=\overrightarrow{a}\cdot \overrightarrow{b}\),求\(f(x)\)在\((0,\dfrac{\pi }{2})\)上的范围。