E is the midpoint of BC.

∴DE is the center line of BC province.

∵BD⊥CD

∴∠BDC=90

∫∠BDC = 90°, and DE is the center line of BC side.

∴BE=DE

Similarly, AE=BE

∴AE=DE

∫∠ADE = 60

△ ade is equilateral.

∴AD=DE