AB//CD,CE平分∠ACD交AB于E,∠A=108°,则∠AEC等于多少度?

题目

AB//CD,CE平分∠ACD交AB于E,∠A=108°,则∠AEC等于多少度?

答案

∠AEC=36°,AB//CD,则是∠AEC=∠ECD=∠ACE,根据平行同旁内角互补（∠A=108°）.则∠ACD=180-108=72=2∠AEC=2∠ECD=2∠ACE,所以∠ACE=36