grandes-ecoles 2010 QIV.A.1

grandes-ecoles · France · centrale-maths2__mp Proof Direct Proof of a Stated Identity or Equality
We wish to prove the Cartan-Dieudonné theorem, whose statement is: ``if $f \in O(E,q)$, $f$ is the composition of at most $n$ reflections, where $n = \operatorname{dim}(E)$, with the convention that $\operatorname{Id}_E$ is the composition of 0 reflections.''
Prove the Cartan-Dieudonné theorem when $n = 1$.
We wish to prove the Cartan-Dieudonné theorem, whose statement is: ``if $f \in O(E,q)$, $f$ is the composition of at most $n$ reflections, where $n = \operatorname{dim}(E)$, with the convention that $\operatorname{Id}_E$ is the composition of 0 reflections.''

Prove the Cartan-Dieudonné theorem when $n = 1$.