AE=BEDE⊥AB∴三角形ADE≌BDE (边角边)∴∠DBE=∠A=30°∴∠CBD=∠DBE=30°∴三角形BDE≌BDC (角边角)CD=DE=2AD=2DE=4AC=AD+CD=6∠ADB=180°-∠A-∠DBE=120°