20 10 the process of solving junior high school math problems in Henan province 15.
15、(20 10? Henan) as shown in the figure, in Rt△ABC, ∠ c = 90, ∠ ABC = 30, AB = 6. Point D is on the side of AB, point E is on the side of BC (not coincident with points B and C), and DA=DE, then the value range of AD is