10.
\((1)\)已知角\(α\)的终边上一点\(P(1,-2)\),则\( \dfrac{\sin α+2\cos α}{\sin α-\cos α} =\) .
\((2)\)已知\( \overrightarrow{a}, \overrightarrow{b} \)是夹角为\(60^{\circ}\)的两个单位向量,则\(\left| \overrightarrow{a}+ \overrightarrow{b}\right| =\) .
\((3)\)若向量\( \overrightarrow{a}=\left(1,1\right) \)与\( \overrightarrow{b}=\left(λ,-2\right) \)的夹角为钝角,则\(λ\)的取值范围是________.
\((4)\)在平行四边形\(ABCD\)中,\(AC\)与\(BD\)交于点\(O\),\( \overrightarrow{DE}= \dfrac{1}{2} \overrightarrow{DO} \),\(CE\)的延长线与\(AD\)交于点\(F\),若\( \overrightarrow{CF}=λ \overrightarrow{AC}+μ \overrightarrow{BD} (λ,μ∈R)\),则\(λ+μ=\)______