我们发现月球环绕地球的轨道总是圆周形--或很近似圆周形。 每一个月，或者更确切些说是每27又1/3天就环绕地球转一圈。
We find that it is traveling in a circle - or very nearly a circle - round the earth, going completely round once a month, or, more exactly, once very 27 1/3 days.
按照数学家们的分类，三叶形是最简单的纽结。 所谓纽结，它是三维空间中不与自己相交的封闭曲线，或者说是三维空间中与圆周同胚的图形。
The trefoil is the simplest knot in mathematicians' classification.
这一环形交叉的圆周长度大约是3.4公里，环绕交叉的道路是波斯兰苏丹萨拉赫丁阿卜杜勒阿齐兹沙阿路。
The circumferential length of this roundabout is approximately 3.4km, and the road that circumvents it is Persiaran Sultan Salahuddin Abdul Aziz Shah. (Link).
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