1957 AMC 12 第 18 题
先试着解答 1957 AMC 12 第 18 题，然后核对你的答案与精心整理的解答，解答来自 LIVE by Po-Shen Loh。你也可以参加完整限时模拟考试、查看全部 1957 AMC 12 解答，或核对答案。
所有题目均经美国数学协会（MAA）官方合法授权使用。
18.
圆 的直径 与 互相垂直。任意弦 与 交于 。则 等于：
Circle has diameters and perpendicular to each other. is any chord intersecting at Then is equal to:
小提示：
因为 是直径，所以角 是直角
Because is a diameter, angle is a right angle
大提示：
比较直角三角形 与
Compare right triangles and
解答：
角 与 都是直角，且两个三角形共有角 。因此三角形 与 相似。由对应边可得 所以 。
因此，正确答案是 B。
Angles and are both right angles, and the two triangles share angle Therefore triangles and are similar. Corresponding sides give Hence
Thus, the correct answer is B.
其他年份的第 18 题
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