These observations allow one to formalize the definition of reflection: a reflection is an involutive isometry of an Euclidean space whose set of fixed points is an affine subspace of codimension 1.
这些观察允许我们形式化反
定义: 反是欧几里得空间
等距同构，它不动
集是余维度为 1 
空间。
观
；若发现问题，欢迎向我们指正。
