圆的周长

圆的周长和直径的比是常数。

Diameter of root circular-arc juncture circle the velocity of light is a constant .

师：圆的周长的计算方法，用字母公式表示。

Teacher : Express the way of calculating the perimeter of a circle by letters .

圆周率，即圆的周长与其直径之比，是数学中最重要的常数之一。

Pi ， the ratio of the circumference of a circle to its diameter , is a very im-portant constant in mathematics .

它听起来很简单，圆的直径除以周长就等于圆周率。

It sounds simple : Pi equals the circumference of a circle divided by its diameter .

椭圆管的长短轴之比为2.25，与圆管具有相同的周长。

The ratio of the long axis over the short one of the oval tube is 2.25 with the same perimeter length as the round tube .

进一步熟记圆的概念，区分圆的周长和面积。

To further understand the concept of a circle , distinguish the perimeter and the area of a circle .

生：围成圆的曲线的长度叫做圆的周长。圆的周长和直径的比是常数。

Students : The length of the curve making a circle is called the perimeter . the velocity of light is a constant .