4.
在平面直角坐标系\(xOy\)中,已知向量\( \overrightarrow{m}=( \dfrac { \sqrt {2}}{2},- \dfrac { \sqrt {2}}{2})\),\( \overrightarrow{n}=(\sin x,\cos x)\),\(x∈(0, \dfrac {π}{2})\).
\((1)\)若\( \overrightarrow{m}⊥ \overrightarrow{n}\),求\(\tan x\)的值;
\((2)\)若\( \overrightarrow{m}\)与\( \overrightarrow{n}\)的夹角为\( \dfrac {π}{3}\),求\(x\)的值.