12. As shown in the figure, in quadrilateral $\mathrm{ABCD}$, $\mathrm{AC}$ and $\mathrm{BD}$ intersect at point $\mathrm{O}$. Draw the altitude $\mathrm{DE}$ of triangle $\mathrm{DBC}$, and connect $\mathrm{AE}$. If the area of triangle $\mathrm{ABO}$ is equal to the area of triangle $\mathrm{DCO}$, and $\mathrm{DC}=17$ cm, $\mathrm{DE}=15$ cm, then what is the area of the shaded part in square centimeters?