Question

如图所示,AB=AC,F,E分别在AB,AC上,BE,CF交于点D,BD=CD求证1 DE=DF 2 角ABD=角ACD

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Answer 1

BD=CD----△BCD是等腰三角形-----∠DCB=∠DBC

AB=AC------∠ABC=∠ACB----BC是公共边-----△BCF≌△CBE------BE=CF-----BE-BD=CF-CD--------DE=DF

△BCF≌△∠CBE------∠ABD=∠ABC-∠CBD         ∠ACD=∠ACB-∠DCB----------

∠ABD=  ∠ACD(等量减等量)