9. Let $f(x)$ be an odd function defined on $\mathbf{R}$. If for any real number $x$, $f(x+2)=-f(x)$, and when $x \in[0,1]$, $f(x)=2 x$, then $f(10 \sqrt{3})=$ $\qquad$
$\begin{array}{l}\text { Two } 9.36-20 \sqrt{3} \text {. } \\ \text { From } f(x+2)=-f(x) \\ \Rightarrow f(x+4)=f(x) \\ \Rightarrow \text { the period of } f(x) \text { is } 4 \\ \Rightarrow f(10 \sqrt{3})=f(10 \sqrt{3}-16) \\ =-f(16-10 \sqrt{3})=f(18-10 \sqrt{3}) \\ =36-20 \sqrt{3} .\end{array}$