AD是△ABC的内角平分线,AD的垂直平分线EM交BC的延长线于E,连结AE.求证：角B=角EAC.

题目

AD是△ABC的内角平分线,AD的垂直平分线EM交BC的延长线于E,连结AE.求证：角B=角EAC.

答案

EM垂直平分AD =>EA=ED =>∠EAD=∠EDA =>∠EAC+∠CAD=∠EDA =>∠EAC+∠DAB=∠EDA ∵∠EDA=∠B+∠D...