9. Let $y=f(x)$ be an odd function on $(-\infty,+\infty)$, $f(x+2)=-f(x)$, and when $-1 \leqslant x \leqslant 1$, $f(x)=x^{3}$.
(1) Find the analytical expression of $f(x)$ when $x \in[1,5]$;
(2) If $A=\{x \mid f(x)>a, x \in \mathbf{R}\}$, and $A \neq \varnothing$, find the range of real number $a$.
9. (1) $f(x+4)=-f(x+2)=f(x)$, so $f(x)$ is a periodic function with a period of 4. That is, $f(x)=$ $\left\{\begin{array}{ll}-(x-2)^{3}, & x \in[1,3) ; \\ (x-4)^{3}, & x \in[3,5] .\end{array}\right.$
(2) When $x \in[1,5)$, $|f(x)| \leqslant 1$. Since $f(x)$ is a periodic function with a period of 4, for $x \in \mathbf{R}$, $|f(x)| \leqslant 1$. Therefore, when $a<1$, $A \neq \varnothing$.