8.
\((1)\)在\(∆ABC \)中,若\({\sin }^{2}A+{\sin }^{2}B < {\sin }^{2}C \),则\(∆ABC \)的形状是_______
\((2)\)在\(∆ABC \)中,角\(A\),\(B\),\(C\)所对的边分别为\(a\),\(b\),\(c\),若三角形面积\(S= \dfrac{ \sqrt{3}}{4}\left({a}^{2}+{b}^{2}-{c}^{2}\right) \),则角\(C=\)
\((3)\)在数列\(\{\)\(a_{n}\)\(\}\)中,其前\(n\)项和为\({S}_{n} \),已知\(a\)\({\,\!}_{1}=1\),\(a_{n}\)\(=2{S}_{n-1} \) \((\)\(n\)\(\geqslant 2\),\(n\)\(∈N^{*})\),这个数列的通项公式是________.
\((4)\)已知\({S}_{n} \)是等差数列\(\left\{{a}_{n}\right\} \)的前\(n\)项和,且\({S}_{6} > {S}_{7} > {S}_{5} \),给属下列五个命题:\(①d < 0 \);\(②{S}_{11} > 0 \);\(③\)使得\({S}_{n} > 0 \)最大的\(n\)值是\(12\);\(④\)数列\(\left\{{S}_{n}\right\} \)中最大项为\({S}_{12} \);\(⑤\left|{a}_{6}\right| > \left|{a}_{7}\right| \),其中正确的命题的序号是 .