15．已知:如图.为上一点.点分别在两侧．..．求证:． [解析] . ．·························································——青夏教育精英家教网—

15．已知:如图.为上一点.点分别在两侧．..．求证:． [解析] . ．·································································································· 2分在和中. ．························································································ 4分．·································································································· 5分 [点评] 本题是一道很简单的全等证明.纵观近几年北京市中考数学试卷.每一年都有一道比较简单的几何证明题:只需证一次全等.无需添加辅助线.且全等的条件都很明显.本题是解答题中几何的第1道题.难度较小是为了让所有的考生在进入解答题后都有一个顺利的开端.避免产生畏惧心理.这样考试才有信心做后面较难的题目. 本题考点:全等三角形的判定(SAS)和性质. 难度系数:0.9 【查看更多】

(本小题满分12分)

如图，已知直线PA交⊙0于A、B两点，AE是⊙0的直径．点C为⊙0上一点，且AC平分∠PAE，过C作CD⊥PA，垂足为D。

(1)求证：CD为⊙0的切线；

(2)若DC+DA=6，⊙0的直径为l0，求AB的长度.

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(本小题满分12分)
如图，已知直线PA交⊙0于A、B两点，AE是⊙0的直径．点C为⊙0上一点，且AC平分∠PAE，过C作CD⊥PA，垂足为D。
(1)求证：CD为⊙0的切线；
(2)若DC+DA=6，⊙0的直径为l0，求AB的长度.