[填空题]
The following diagram showsu)wu3 dx+m*6n;2jw 0 y8vqjgob j/ dcb ahbgh(j c*x) bgnuud 2--wx.*e right-angled triangle $\mathrm{ABC}$ and a sector ABD of a circle with centre $\mathrm{A}$ . The point $\mathrm{E}$ lies on [AC] such that [BE] is perpendicular to [AC]. The region R is bounded by [DE], [BE] and arc BFD.