3．
\((1)\sin 20^{\circ}·\cos 10^{\circ}-\cos \;160^{\circ}·\sin 10^{\circ}= \)_________
\((2)\)如图，函数\(y=f\left(x\right) \)的图象在点\(p\)处的切线方程是\(y=-2x+9 \)，则\(f\left(4\right)+{f}^{{{{'}}}}\left(4\right) \)的值为__________．
\((3)\)在极坐标系中，直线\(ρ\cos θ- \sqrt{3}ρ\sin θ-1=0 \)与圆\(ρ=2\cos θ \)交于\(A\)，\(B\)两点，则\(\left|AB\right|= \)__________
\((4)\)已知定义在\(R\)上的函数\(f\left(x\right),g\left(x\right) \)满足\(\dfrac{f\left(x\right)}{g\left(x\right)}={a}^{x} \)，且\({f}^{{{{'}}}}\left(x\right)g\left(x\right) < f\left(x\right){g}^{{{{'}}}}\left(x\right) \)，\(\dfrac{f\left(1\right)}{g\left(1\right)}+ \dfrac{f\left(-1\right)}{g\left(-1\right)}= \dfrac{5}{2} \)，若有穷数列\(\left\{ \dfrac{f\left(n\right)}{g\left(n\right)}\right\}\left(n∈{N}^{*}\right) \)的前\(n\)项和等于\(\dfrac{31}{32} \)，则\(n\)等于____．