1.
设\( \overrightarrow{a}=\left(\cos α,\left(λ-1\right)\sin α\right), \overrightarrow{b}=\left(\cos β,\sin β\right),\left(λ > 0,0 < α < β < \dfrac{π}{2}\right) \)是平面上的两个向量, 若向量\( \overrightarrow{a}+ \overrightarrow{b} \)与\( \overrightarrow{a}- \overrightarrow{b} \)互相垂直.
\((\)Ⅰ\()\) 求实数\(λ \)的值\(;\)
\((\)Ⅱ\()\)若\( \overrightarrow{a}· \overrightarrow{b}= \dfrac{4}{5} \), 且\(\tan β= \dfrac{4}{3} \), 求\(\tan \alpha \)的值.