为什么车轮子都是圆形的呢?能不能是三角形的?因为在同一个圆内,从圆上任意一点到圆心的距离是相等的,也就是一个圆的所有半径都相等,所有直径也都相等。所以圆形的车轮滚动起来才平稳。而三角形不具有这些特点,滚动起来会上下起伏。哦!我明白了。难怪所有的轮子都是圆形的。可是怎样计算轮子滚动一圈的长度呢?轮子滚动一圈的长度其实就是圆的周长。围成圆的曲线的长度叫圆的周长,圆的周长总是比它的直径的3倍多一 Why wheels are round? Can it be a triangle? Because in the same circle, from any point on the circle to the center of the distance is equal, that is, a circle of all the same radius, all the diameters are equal. So round the wheels rolled up smoothly. The triangle does not have these characteristics, rolling up and down. Oh I see. No wonder all the wheels are round. But how to calculate the length of the wheel rolling it? The length of the wheel rolling circle is actually the circumference of the circle. The length of the curve enclosed in a circle is called the circumference of a circle whose circumference is always more than three times its diameter