[填空题]
The following diagram shows8h*knnycc/ k8 a right8(aq6j)u zvdg -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.