circular side rule

例句：

1. 1. Thecircle of light cast by the moon isbeautiful.
   月亮投下的光圈很美丽。
2. 2.The car's tires are circular inshape.
   汽车的轮胎是圆形的。
3. 3. Thecircle of friends we have formed is verytight.
   我们形成的朋友圈非常紧密。