9.
\((1)\)已知\(a > 0\),\({{\left( \dfrac{a}{\sqrt{x}}-x \right)}^{6}}\)展开式的常数项为\(15\),则\(\int_{-a}^{a}{(}\sqrt{{1}-{{x}^{2}}}+\sin {2}x){d}x=\)________.
\((2)\)已知向量\(a\),\(b\)满足:\(|a|=|b|=1\),且\(a\cdot b=\dfrac{1}{{2}}\),若\(c=xa+yb\),其中\(x > 0\),\(y > 0\)且\(x+y=2\),则\(|c|\)的最小值是________.
\((3)\)将正整数\(12\)分解成两个正整数的乘积有\(1×12\),\(2×6\),\(3×4\)三种,其中\(3×4\)是这三种分解中两数差的绝对值最小的,我们称\(3×4\)为\(12\)的最佳分解\(.\)当\(p×q(p\leqslant q\)且\(p\),\(q∈N^{*})\)是正整数\(n\)的最佳分解时,我们定义函数\(f(n)=q-p\),例如\(f(12)=4-3=1.\)数列\(\{f(3^{n})\}\)的前\(100\)项和为________.
\((4)\)如图,正方体\(ABCD-A_{1}B_{1}C_{1}D_{1}\)的棱长为\(3\),在面对角线\(A_{1}D\)上取点\(M\),在面对角线\(CD_{1}\)上取点\(N\),使得\(MN/\!/\)平面\(AA_{1}C_{1}C\),当线段\(MN\)长度取到最小值时,三棱锥\(A_{1}-MND_{1}\)的体积为________.