应该是AB/AC=BD/BC吧?那要怎么做？证明：作CF∥AD，交AB于点F则∠EAD=∠AFC，∠DAC=∠ACF∵AD平分∠EAC∴∠EAD=∠DAC∴∠AFC=∠ACF∴AF=AC∵CF∥AD∴BD/CD=AB/AF∴BD/CD=AB/AC