9.
\((1)\)不等式\(\dfrac{1}{x} < 1\)的解集是________.
\((2)\)已知\(a\),\(b\)是互异的正数,\(A\)是\(a\),\(b\)的等差中项,\(G\)是\(a\),\(b\)的正的等比中项,则\(A\)________\(G( > , < ,\geqslant ,\leqslant \)选填其中一个\()\).
\((3)\)已知\(\sin (60{}^\circ +\alpha )=\dfrac{5}{13}\),\(30^{\circ} < a < 120^{\circ}\),则\(\cos α=\)________.
\((4)\)如图在正方体\(ABCD—A_{1}B_{1}C_{1}D_{1}\)中,给出以下结论
\(①A_{1}C_{1}\)与平面\(A_{1}B_{1}CD\)成\(45^{\circ}\)角;
\(②CD_{1}\)与\(BC_{1}\)成\(60^{\circ}\)角;
\(③{{V}_{B1}}_{-{{A}_{1}}B{{C}_{1}}}=\dfrac{1}{2}{{V}_{B}}{{_{1}}_{-A{{D}_{1}}C}}\);
\(④\)正方体的内切球,与各条棱相切的球,外接球的表而积之比为\(1︰2︰3\)其中正确的结论序号是________\(.(\)写出所有正确结论的序号\()\)