The purpose of this section is to examine square matrices whose columns (or rows) are orthonormal.The standard inner product and the Euclidean 2-norm are the only ones used in this section,so distinguishing subscripts are omitted.
这一部分的目的是examine列向量（或行向量）正交的方阵.这里用到的只有标准的内积和欧几里德2-norm,所以省略了用来区分的下标.
英语不好,只能翻译成这样了.