[填空题]
The following diagrap1p iyn3;kll/c-i-hl aa* df 1mqsspfsb x((52 shows a radioactivity warning symbol made out of a circle in the centre and three equal s5p2sqxf( sb( blades.
$\text { Given that } \mathrm{OA}=2 \mathrm{~cm}, \mathrm{AB}=1 \mathrm{~cm}, \mathrm{BC}=4 \mathrm{~cm} \text {, and } \mathrm{CO} \mathrm{D}=30^{\circ} \text {, find the area of the symbol. }$
