(1) when the circle is tangent to BC, when DE⊥BC,
∫∠ABC = 30,
∴DE= BD,
AB = 6,
∴ad=2;
② When the circle intersects BC, if the intersection point is B or C, then AD= AB=3.
The value range of ∴AD is 2 ≤ AD < 3. Comments: It is the key to solve this problem to distinguish the minimum and maximum ad by using the position relationship between BC and circle.