He qualifies exhumations as a humanitarian act that allows families to close what he calls the circle of pain and mourning in which they have been caught for a quarter of a century, and says it was unthinkable as recently as a few years ago that investigations into war crimes would have been allowed in this country.

VOA: standard.2009.12.18

So that a half circle, instead of calling it 180 degrees, And a quarter circle, instead of 90, It's good to know certain famous angles.

半圆,不说它是180°,四分之一圆,不叫90°,知道一些常用的角度很有必要

耶鲁公开课 - 基础物理课程节选

During this part, when you're doing a quarter of a circle, this is supposed to be a quarter of a circle.

在这部分,当你沿着四分之一圆运动,这就是个一个圆的四分之一

耶鲁公开课 - 基础物理课程节选

Pick a time. Let's say, if I go a quarter of a circle, I expect to be moving to the left.

选一个时间,例如我走四分之一圈,我想向左走

耶鲁公开课 - 基础物理课程节选

Let's take a circle and just keep a quarter of the circle.

我们来画一个圆,只画四分之一圆即可

耶鲁公开课 - 基础物理课程节选