相关beanequilateraltrian的文学知识

问题详情：Infig.1,let beanequilateraltriangle,DandEbepointsonedgesABandACrespectively,FbeintersectionofsegmentsBEandCD,and,thenthemagnituderelationbetweenAdandCEis（   ） A.  B.  C.  D.indefinite...