Question

如图,∠A=½∠ABC,BD平分∠ABC,∠C=30°,求∠ADB的度数

Answer 1

设∠A=x,又∠A=½∠ABC,则∠ABC=2x

又x+2x+30°=180,所以x=50,∠ABC=100

又BD平分∠ABC,所以∠ABD=50,

又∠A+∠ABD+∠ADB=180=50+50+∠ADB

所以∠ADB=80