怎么找到圆心

在求解圆的周长或面积等基础几何题时，通常需要找到一个圆的圆心。阅读本文，了解如何只使用圆规和直尺来找到圆心。

步骤

画一个圆并标注相应的点

1. {"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/9\/90\/Find-the-Center-of-a-Circle-Step-1.jpg\/v4-460px-Find-the-Center-of-a-Circle-Step-1.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/9\/90\/Find-the-Center-of-a-Circle-Step-1.jpg\/v4-728px-Find-the-Center-of-a-Circle-Step-1.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"} 1 使用几何圆规在一张白纸上画一个任意大小的圆。几何圆规用于绘制和测量圆，在大多数零售商店有售。
2. {"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/1\/18\/Find-the-Center-of-a-Circle-Step-2.jpg\/v4-460px-Find-the-Center-of-a-Circle-Step-2.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/1\/18\/Find-the-Center-of-a-Circle-Step-2.jpg\/v4-728px-Find-the-Center-of-a-Circle-Step-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"} 2 使用刻度尺或直尺在圆内画一条水平线，连接圆周上两个不同的点。可在圆的顶部、底部及其他任意位置画水平线。
3. {"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/0\/02\/Find-the-Center-of-a-Circle-Step-3.jpg\/v4-460px-Find-the-Center-of-a-Circle-Step-3.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/0\/02\/Find-the-Center-of-a-Circle-Step-3.jpg\/v4-728px-Find-the-Center-of-a-Circle-Step-3.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"} 3 在水平线与圆周相交处分别标注 A 和 B 点。

找圆心

1. {"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/6\/64\/Find-the-Center-of-a-Circle-Step-4.jpg\/v4-460px-Find-the-Center-of-a-Circle-Step-4.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/6\/64\/Find-the-Center-of-a-Circle-Step-4.jpg\/v4-728px-Find-the-Center-of-a-Circle-Step-4.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"} 1 画两个部分重叠的圆，其中一个以 A 为圆心，另一个以 B 为圆心。确保两个圆部分重叠，类似于韦恩图。
2. {"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/f\/f5\/Find-the-Center-of-a-Circle-Step-5.jpg\/v4-460px-Find-the-Center-of-a-Circle-Step-5.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/f\/f5\/Find-the-Center-of-a-Circle-Step-5.jpg\/v4-728px-Find-the-Center-of-a-Circle-Step-5.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"} 2 通过两个圆相交的两个点，画一条垂线。
3. {"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/c\/ca\/Find-the-Center-of-a-Circle-Step-6.jpg\/v4-460px-Find-the-Center-of-a-Circle-Step-6.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/c\/ca\/Find-the-Center-of-a-Circle-Step-6.jpg\/v4-728px-Find-the-Center-of-a-Circle-Step-6.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"} 3 擦掉您刚才所画的两个圆以简化图形，但请保留交点的字母标注（稍后还需要画 2 个新圆）。
4. {"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/9\/90\/Find-the-Center-of-a-Circle-Step-7.jpg\/v4-460px-Find-the-Center-of-a-Circle-Step-7.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/9\/90\/Find-the-Center-of-a-Circle-Step-7.jpg\/v4-728px-Find-the-Center-of-a-Circle-Step-7.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"} 4 分别以上图中所示的 C 点和 D 点为圆心，用圆规画两个大小相同的圆，即分别以垂线与主圆相交的两点为圆心。
5. {"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/3\/3f\/Find-the-Center-of-a-Circle-Step-8.jpg\/v4-460px-Find-the-Center-of-a-Circle-Step-8.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/3\/3f\/Find-the-Center-of-a-Circle-Step-8.jpg\/v4-728px-Find-the-Center-of-a-Circle-Step-8.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"} 5 通过两个新圆的交点，画一条水平线。此即第二条直径。
6. {"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/b\/b6\/Find-the-Center-of-a-Circle-Step-9.jpg\/v4-460px-Find-the-Center-of-a-Circle-Step-9.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/b\/b6\/Find-the-Center-of-a-Circle-Step-9.jpg\/v4-728px-Find-the-Center-of-a-Circle-Step-9.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"} 6两条直线的交点即圆心！

小提示

• 用绘图纸画图更方便。

警告

• 为了找到圆的真实圆心，您必须使用几何圆规和直尺。
• 直尺与刻度尺不一样，刻度尺上标注有刻度。

你需要准备

• 铅笔
• 纸
• 直尺
• 几何圆规