6.
\((1)\)函数\(f(x)={{\log }_{\frac{1}{2}}}({{x}^{2}}-6x+5)\)的单调递减区间是______________________________.
\((2)\)已知幂函数\(f(x)=({{m}^{2}}-m-1){{x}^{m}}\)在\(x\in (0,+\infty )\)上单调递减,则实数\(m=\)_________.
\((3)\)已知\(\sin (\dfrac{\pi }{4}-x)=-\dfrac{1}{3}\),且\(0 < x < \dfrac{\pi }{2}\),求\(\sin (\dfrac{\pi }{4}+x)\)的值_________。
\((4)\)下列说法:
\(①\)正切函数\(y{=}\tan x\)在定义域内是增函数;
\(②\)函数\(f(x){=}\cos(\dfrac{2}{3}x{+}\dfrac{\pi}{2})\)是奇函数;
\(③x{=}\dfrac{\pi}{8}\)是函数\(f(x){=}\sin(2x{+}\dfrac{5\pi}{4})\)的一条对称轴方程;
\(④\)扇形的周长为\(8{cm}\),面积为\(4cm^{2}\),则扇形的圆心角为\(2{rad}\);
\(⑤\)若\(\alpha\)是第三象限角,则\(\dfrac{{|}\sin\dfrac{\alpha}{2}{|}}{\sin\dfrac{\alpha}{2}}{+}\dfrac{{|}\cos\dfrac{\alpha}{2}{|}}{\cos\dfrac{\alpha}{2}}\)取值的集合为\(\{{-}2{,}0\}\),
其中正确的是__________\(.(\)写出所有正确答案的序号\()\)