It's perfectly reasonable to talk about transformations between dimensions, such as one that takes two D vectors to three D vectors.

谈论维度之间的变换是完全合理的 比如一个从两个D向量到三个D向量的变换。

So just keep him in the back of your If we project two D vectors straight onto this diagonal number line, in effect, we've just defined a function that takes two d vectors to numbers.

所以只要把他放在你的后面如果我们把两个D向量直接投射到这条对角线上 实际上 我们刚刚定义了一个函数它把两个D向量转换成数字。