如图,D是BC延长线上一点,∠ABC、∠ACD的平分线交于E.通过测量∠A、∠E的度数判断∠A与∠E的数量关系.

∵∠DCE=∠E+∠EBC=∠E+1/2∠ABC
∠DCE=1/2∠ACD=1/2(∠ABC+∠A)
∴∠E+1/2∠ABC=1/2∠ABC+1/2∠A
∠E=1/2∠A