Question

如图,在△abc中,ad平分∠bac,be⊥ac于点e 交ad于点f,试说明∠2=1/2(∠abc+∠c)

Answer 1

∠2+∠1=90 [1]

∠ABC+∠C+2∠1=180 [2]

由[1]得 ∠1=90- ∠2 [3]

将[3]代入[2]得

2∠2 =∠ABC+∠C

所以

∠2=1/2（∠ABC+∠C)