AE∠DAE∠BAE即∠EAC∠DAB又∵ABAC，ADAE∴△ABD≌△ACESAS∴BDCE∠ADB∠AEC又∵∠ADE∠AED90°∴∠AEC∠CDE∠AED90°即∠DCE90°∴CE⊥DC∴CE⊥BD9分
9
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