BDE=∠ADB
∴△BDE∽△ADB
∴BD/DE=AD/BD
DE*AD=BD？
Similarly, DE*AD=CD?
∴BD？ =CD？
②∵CE⊥AD
∴∠CEA=90
∠∠ACB = 90°
∠DAC=∠CAE
∴△DAC∽△CAE
DE/CD=AD/CD
D is the midpoint.
∴BD=CD
∴DE/BD=AD/BD
∠∠BDE =∠ADB