9. As shown in the figure below, $\mathrm{AB}$ is the diameter of a semicircle, $\mathrm{O}$ is the center of the circle, arc $\mathrm{AC}=$ arc $\mathrm{CD}=$ arc $\mathrm{DB}, \mathrm{M}$ is the midpoint of arc $\mathrm{CD}$, $\mathrm{H}$ is the midpoint of chord $\mathrm{CD}$, if $\mathrm{N}$ is a point on $\mathrm{OB}$, and the area of the semicircle is 12 square centimeters, then the area of the shaded part in the figure is ( ) square centimeters.
$2$