Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Possible Duplicate:
Are isometric normed linear spaces isomorphic?
$ f: \mathbb{R}^n \to \mathbb{R}^m $ preserving distances

Consider the set of all functions $\varphi : \mathbb{R}^n \rightarrow \mathbb{R}^n$ that preserve distance.

That is $\forall a,b : \| a-b\| = \|\varphi(a) - \varphi(b)\| $

Is the following statement true or false?

$\forall \varphi: \exists v \in \mathbb{R}^n, M \in \mathbb{R}^{n\times n}: \varphi(x) = Mx + v$

Why or why not? (ie rough sketch of proof)

share|cite|improve this question

marked as duplicate by Arturo Magidin, Gerry Myerson, Benjamin Lim, copper.hat, t.b. May 16 '12 at 7:27

This question was marked as an exact duplicate of an existing question.

This is a repeat of this question – Arturo Magidin May 16 '12 at 5:55
And indeed, $M$ must be orthogonal. Presumably the distance is the $2$-norm. – copper.hat May 16 '12 at 5:59
See also this question – t.b. May 16 '12 at 7:28