∵AC＝AB∵∠ABC＝∠C＝∠D∵∠ABC＝∠D,∠BAD＝∠DAB∴⊿ABE∽⊿ADB∴AB/AD＝AE/ABAB²＝AD·AE＝﹙AE＋ED﹚·AE＝﹙8＋2﹚×8＝80∴AC＝AB＝√80＝4√5
证相似。。
