“圆”是平面几何的最后一章,它既是平几的终了曲,又是平几的高潮,这一部分可谓内容丰富,综合性强,题型广泛,方法灵活,因此在数学竞赛中占有相当突出的地位,成为其热点之一。下面谈谈与圆有关的经常涉及的几类问题:1 一般性问题这里所说的一般性问题,系指依直线与圆的位置关系而出现的涉及线段、角的计算,直线或线段的相互关系的判定,线段间的比例式、乘积式的证明等。 “Circle” is the last chapter of plane geometry. It is not only the final song of a few lines, but also the climax of a few lines. This part can be described as rich in content, comprehensive in synthesis, wide in question type, flexible in method, and therefore occupies a considerable amount in mathematical competitions. Prominent status has become one of its hot spots. Here are some of the frequently-related issues related to circles: 1 General issues The general issues mentioned here refer to the calculations involving line segments and angles, depending on the positional relationship between lines and circles, and the mutuality of lines or line segments. Judgment of relations, ratios between line segments, proof of multiplications, etc.