角DAE=1/2(角C-角B）,理由如下
90°=∠DAE+∠AED°
=∠DAE+∠EAC+∠C
=∠DAE+1/2∠BAC+∠C
=∠DAE+1/2(180°-∠A+∠C)+∠C
整理即∠DAC=1/2(∠C-∠B）
望采纳