(1)由题设,∠BAC=∠DAC.AB/AC=AC/AD.===>△ABC∽△ACD.（两边对应成比例,夹角相等的两三角形相似）===>∠B=∠ACD.(相似三角形对应角相等）.又∠B=∠AEF,===>∠ACD=∠AEF(等量代换）.===>四点A,E,C,F共圆.（四点共圆的条件）.===>∠AFE=∠ACB.(同弧上的圆周角相等）.（2）由∠B=AEF,∠ACB=∠AFE.===>△ABC∽△AEF.===>AB/AE=BC/EF.===>AB/BC=AE/EF.请再看看答案.
(1)由题设,∠BAC=∠DAC.AB/AC=AC/AD.===>△ABC∽△ACD.（两边对应成比例,夹角相等的两三角形相似）===>∠B=∠ACD.(相似三角形对应角相等）.又∠B=∠AEF,===>∠ACD=∠AEF(等量代换）.===>四点A,E,C,F共圆.（四点共圆的条件）.===>∠AFE=∠ACB.(同弧上的圆周角相等）.（2）由∠B=AEF,∠ACB=∠AFE.===>△ABC∽△AEF.===>AB/AE=BC/EF.===>AB/BC=AE/EF.请再看看答案.