grandes-ecoles 2010 QIV.B.1

grandes-ecoles · France · centrale-maths2__mp Not Maths
We propose to prove Witt's theorem, whose statement is: ``let $F$ and $F'$ be two vector subspaces of $E$ such that there exists an isometry $f$ from $(F, q_{/F})$ to $(F', q_{/F'})$. Then there exists $g \in O(E,q)$ such that $g_{/F} = f$.''
Show that we can reduce to the case where $F$ and $F'$ are non-singular.
We propose to prove Witt's theorem, whose statement is: ``let $F$ and $F'$ be two vector subspaces of $E$ such that there exists an isometry $f$ from $(F, q_{/F})$ to $(F', q_{/F'})$. Then there exists $g \in O(E,q)$ such that $g_{/F} = f$.''

Show that we can reduce to the case where $F$ and $F'$ are non-singular.