首先翻折可知AB=AC=AD=5所以∠B=∠ACB=∠ACD=∠ADC∴∠BAC=∠CAD=180-∠B-∠ACB=180-2∠B∠DCE=180-∠ACD-∠ACB=180-2∠B∴∠DCE=∠CAD∵∠E=∠E∴△DCE∽△CAE所以DE:CE=CE:AE因为DE=AE-AD=9-5=4所以DE:CE=CE:AE→4：CE=CE：9CE^2=36CE>0所以CE=6
