题目

At Sam’s birthday party he had many guests, who were ________friends of his. A. mostly      B. usually     C. specially           D. nearly 答案：A 解析: 略　　如下图，△ABC的高AD与CE交于点F且AD＝CD． 　　求证：(1)AB＝CF 　　(2)当AE＝CF时△ABC是等腰三角形．