Yeah, if you immediately said, "Well, if the vector is , then the vector looks like this.", you're making the assumption that I am writing the vector in terms of i and j.

对,如果你紧接着就说," 如果一个矢量是,那么它就像这样 ",你其实就是假设了,我是按 i 和 j 分量的形式写的这个矢量

耶鲁公开课 - 基础物理课程节选