7.
如图,在直三棱柱
\(ABC\)\(\)
\(A\)\({\,\!}_{1}\)
\(B\)\({\,\!}_{1}\)
\(C\)\({\,\!}_{1}\)中,
\(AB\)\(=1\),
\(AC\)\(=\)
\(AA\)\({\,\!}_{1}= \sqrt{3}\),\(∠\)
\(ABC\)\(=60^{\circ}\).
\((1)\)证明:\(AB\)\(⊥\)\(A\)\({\,\!}_{1}\)\(C\);
\((2)\)求二面角\(A\)\(\)\(A\)\({\,\!}_{1}\)\(C\)\(\)\(B\)的正切值大小.