\((1)\)在等腰\(\Delta ABC\)中,\(AB=AC\),\(BC=6\),点\(D\)为边\(BC\)的中心,则\(\overrightarrow{AB}\cdot \overrightarrow{BD}=\)_________.
\((2)\)设\(x\),\(y\)满足约束条件\(\begin{cases} & 2x+y-1\leqslant 0 \\ & x+2y+1\geqslant 0 \\ & x-y+1\geqslant 0 \end{cases}\),则\(z=2x-3y\)的最大值为_________.
\((3)\)设函数\(f(x)(m\in R)\)满足\(f(x-\pi )=f(x)-\sin x\),当\(-\pi < x\leqslant 0\)时,则\(f(\dfrac{2018\pi }{3})=\)_________\(..\)
\((4)\)椭圆的左、右焦点分别为\({F}_{1},{F}_{2} \),弦\(AB\)过\({F}_{1} \),若\(∆AB{F}_{2} \)的内切\(\dfrac{{{x}^{2}}}{36}+\dfrac{{{y}^{2}}}{20}=1\)圆周长为\(2\pi \),\(A\),\(B\)两点的坐标分别为\(\left({x}_{1},{y}_{1}\right) \)和\(\left({x}_{2},{y}_{2}\right) \),则\(\left| {{y}_{2}}-{{y}_{1}} \right|=\)___________.