由AB=AC,DB=DC且AD=AD,故△ABD全等于△ADC,
故角BAD=角DAC,又AB=AC,AE=AE,故△ABE全等于△ACE.
故BE=EC,
角AEB=角AEC=90°,即AE垂直BC.
△ABC为等腰三角形,E为底边中点,D为AE上一点.
由AB=AC,DB=DC且AD=AD,故△ABD全等于△ADC,
故角BAD=角DAC,又AB=AC,AE=AE,故△ABE全等于△ACE.
故BE=EC,
角AEB=角AEC=90°,即AE垂直BC.
△ABC为等腰三角形,E为底边中点,D为AE上一点.