∠ADB=90°
∠BDC=∠BAC
∠BDC+∠ADE=90°=∠ADE+DAE
所以∠DAE=∠BAC
∠E=∠ACB=90°
所以△EAD∽△CAB
ED/CB=AD/AB=1/√2
ED=3/√2
tan∠DAE=ED/AE=3/8