Question

如图AB=AC,∠BAC=a(阿拉法）,D是△ABC外一点,则∠BDC满足什么条件时,∠BDA=∠CDA

Answer 1

答：当∠BDC=180º－α条件时,∠BDA=∠CDA证明：作AE⊥BD,AF⊥CD则∠AEB=∠AFC=90º∵∠BDC=180º－α∴∠ABD+∠ACF=360º-∠BDC-∠BAC=180º又∠ABD+∠ABE=180º∴∠ABE=∠ACF,又AB=AC∴△...