平面向量\( \overrightarrow{a}=\left(3,-4\right), \overrightarrow{b}=\left(2,x\right), \overrightarrow{c}=\left(2,y\right) \)已知\( \overrightarrow{a} /\!/ \overrightarrow{b} \),\( \overrightarrow{a}⊥ \overrightarrow{c} \),
\((1)\)求向量\( \overrightarrow{b} \)和向量\( \overrightarrow{c} \)
\((2)\)求\( \overrightarrow{b} \)与\( \overrightarrow{c} \)夹角。