穹顶之下问题---**Question Stem:** 下图中的点B、C、D、E为半圆弧的五等分点，直径AF长为10厘米，求阴影部分面积。 (Translation: In the figure below, points B, C, D, and E are the five equal division points of the semicircle arc, the diameter AF is 10 cm long, find the area of the shaded part.) **Chart Description:** * **Type:** Geometric diagram (semicircle with points on the arc and lines from one endpoint of the diameter). * **Main Elements:** * A semicircle arc is shown above a horizontal diameter AF. * Point A is the left endpoint of the diameter, and point F is the right endpoint. * Point O is located on the diameter AF, marked with a red dot, representing the center of the semicircle. * Points B, C, D, and E are located on the semicircle arc, dividing it into five equal parts (arc AB, arc BC, arc CD, arc DE, arc EF). * Line segments connect point A to points B, C, D, and E. * Segments AB, AC, AD, AE are lines originating from A. * Lines AC and AD are represented as dotted lines. * Two regions are shaded: * The region bounded by the line segments AB and AC and the arc BC is shaded with diagonal lines. * The region bounded by the line segments AD and AE and the arc DE is shaded with horizontal lines. * **Labels:** Points A, B, C, D, E, F, O are labeled. * **Dimensions:** The length of the diameter AF is given as 10 centimeters.