1. Given that the function $y=f(x)$ is a periodic function with a period of 3 defined on $\mathbf{R}$, Figure 1 shows the graph of this function in the interval $[-2,1]$. Then the value of $\frac{f(2010)}{f(5) f(16)}$ is equal to
$-\sqrt{1}-\frac{1}{2}$.
Note that
$$
\begin{array}{l}
f(5)=f(-1)=-1, \\
f(16)=f(1)=2, \\
f(2010)=f(0)=1 . \\
\text { Then } \frac{f(2010)}{f(5) f(16)}=-\frac{1}{2} .
\end{array}
$$