贴出的答案有误,请参考如下过程:(1)证明:∵∠ADE+∠BFE=180°又∵四边形GDEF内角和为360°∴∠FGD+∠FED=180°又∵∠FGD+∠AGF=180°∴∠BEF=∠FED=∠AGF(2)解:取在AC上取H,使得AH=AG∵AD=AF∠HAD=∠GAFAH=AG∴△HAD≌△GAF∴GF=DH,∠AHD=∠AGF又∵∠FED=∠AGF∴∠FED=∠AHD∴∠FEC=∠CHD又∵∠C=∠C∴△FEC∽△DHC∴CF:FE=CD:HD又∵CF=BF,GF=DH∴BF:EF=CD:GF=k