△ The base of △adb is ad=8- 1=7(cm), and the corresponding height of the base ad is 6-2 = 4 (cm).

Delta △adb area = 7 * 4/2 =14 (cm2);

Similarly, calculate the area of △adc.

Delta △adc's bottom ad=8- 1=7(cm), and the corresponding height of bottom ad is 5-2 = 3 (cm).

△ The area of △adb = 7 * 3/2 = 21/2 (cm2); ;

By shadow area = △ ADB area-△ ADB area

= 14-2 1/2

=7/2

= 3.5(cm2)；

Area of shaded part = 3.5 (cm2);