![](https://www.ebk.net.cn/tikuimages/2/2016/700/shoutiniao57/0898909af673df9d6603e33dfe8b449a.png)
如图,在\(xoy\)平面上,点\(A(1,0)\),点\(B\)在单位圆上,\(∠AOB=θ(0 < θ < π)\)
\((1)\)若点\(B(- \dfrac {3}{5}, \dfrac {4}{5})\),求\(\tan ( \dfrac {θ}{2}+ \dfrac {π}{4})\)的值;
\((2)\)若\( \overrightarrow{OA}+ \overrightarrow{OB}= \overrightarrow{OC}\),四边形\(OACB\)的面积用\(S_{θ}\)表示,求\(S_{θ}+ \overrightarrow{OA}⋅ \overrightarrow{OC}\)的取值范围.