I do not know whether you realize it, but this condition is essential to us.
我不知道你是否了解,但是,这个条件对我们是必要的。
Instruments have been devised and can be so placed that all three elements can be recorded in different graphs.
已经设计出了一些仪器,它按照一定的安放方式就可测绘出这三种运动的曲线图。