11. (12 points) In the figure, by connecting every other vertex of a regular octagon with each side measuring 12 cm, two squares can be formed. The area of the shaded region in the figure is $\qquad$ square centimeters.
11. (12 points) In the figure, by connecting every other vertex of a regular octagon with each side length of 12 cm, two squares can be formed. The area of the shaded part in the figure is _288_ square centimeters.
【Solution】Solution: According to the analysis, the shaded area can be decomposed into eight equal (rotationally symmetric) triangles, with a base of 12. Draw the height as shown in the figure. It is not difficult to see that the two triangles in the figure are exactly the same (string diagram), thus $h=\frac{12}{2}=6$, the area of the shaded part is: $S=\frac{12 \times 6}{2} \times 8=288$. Therefore, the answer is: 288.