Entry Nº 055Stage 3 · Grades 5–6图形与几何
圆
到定点距离相等的点组成的图形；一中同长。
This page has no English version yet — the original Chinese text is shown below.
Definition
平面上**到定点（圆心）距离都等于定长（半径）**的点，围成圆。古人说「圆，一中同长也」。直径是半径的 2 倍，圆有无数条对称轴——它是最完美的平面图形。
Where it comes from · where it goes
Prerequisites
What builds on it