我可以在平面内自由移动。

I can freely move around the plane.

youdao

可以沿着曲线移动，在平面内的曲线移动。

I can move in the line, in the line in a plane.

youdao

反射对称就是一种镜子效映，一个物体在平面内反射后得到另一个自已。

It is the "mirror" effect, or when one object is reflected across a plane to create another instance of itself.

youdao

Particle's moving in a plane.

物体在平面内运动

耶鲁公开课 - 基础物理课程节选

Then, I gave you one other very important example of a particle moving in the x-y plane.

下面我再拿一个重要的例子,质点在 x-y 平面内的运动

耶鲁公开课 - 基础物理课程节选

Our picture now is going to be some particle that's traveling in the x-y plane.

我们现在的情景是在 x-y 平面内,运动的质点

耶鲁公开课 - 基础物理课程节选