CD是三角形ABC的外角---角ACE的平分线,CD与BA的延长线交于点D,比较角BAC与角B的大小,说明理由

∠BAC 比 ∠B大
因为
∠ACD = (1/2)∠ACE = (1/2)(∠BAC+∠B)
∠BAC = ∠D + ∠ACD = ∠D + (1/2)(∠BAC+∠B)
(1/2)(∠BAC) = ∠D + (1/2)∠B
∠BAC = 2∠D + ∠B
∠BAC - ∠B = 2∠D>0