(1)∵ADDB=AEEC,∴ADAB=AEAC,又∵∠A=∠A,∴△ADE∽△ABC,∴∠ADE=∠B,∴DE∥BC,∴ABDB=ACEC;(2)∵AC=3,EC=1,∴AE=AC-EC=2,∴ADDB=AEEC=2,∴S△ACDS△BCD=ADBD=2,∴S△ACD=2S△BCD,∵S△ABC=S△... (1)先根据比例的性质得出 AD AB= AE AC,再由两组对应边的比相等,且夹角相等...