OA split cab

∴∠OAB=∠OAC

∠∠OEA =∠ODA = 90。

OA=OA

∴△OEA≌△ODA

∴OE=OD

(1) ∵ The distance from the point on the angle dividing line to both sides of the angle is equal.

∴DE=DC=CB-BD=4

② Equality

∠∠B = 30

∴∠BAC=60

And ∵AD is the bisector of ∠BAC.

∴∠DAB=60 /2=30 =∠B

△DAB is an isosceles triangle with AD=BD.