这道题怎么做？请像老师一样讲给我听---**Question Number:** 16
**Question Stem:**
如图, △ABC 为等边三角形, 点 D 为 △ABC 外的一点, ∠ADC=60°, AD=8, BD=4√7, 则 △BCD 的面积为_____.
(As shown in the figure, △ABC is an equilateral triangle, point D is a point outside △ABC, ∠ADC=60°, AD=8, BD=4√7, then the area of △BCD is _____.)
**Diagram Description:**
* **Type:** Geometric figure.
* **Main Elements:**
* Four points labeled A, B, C, and D.
* Lines connecting A to B, B to C, C to A, A to D, B to D, and C to D, forming triangles ABC, ABD, ACD, and BCD.
* Triangle ABC appears as a triangle with vertices A, B, C.
* Point D is positioned outside the apparent area of triangle ABC.
* Vertex labels A, B, C, and D are placed near the respective points.
**Options:**
None provided in the image. The question asks for a fill-in-the-blank answer.