Section CfDotOrthonormal.
Variables (M : {group gT}) (S : seq 'CF(G)) (nu : 'CF(G) -> 'CF(M)).
Hypotheses (Inu : {in 'Z[S] &, isometry nu}) (onS : orthonormal S).
Let oSS := orthonormal_orthogonal onS.
Let freeS := orthogonal_free oSS.
Let nS1 : {in S, forall phi, '[phi] = 1}.

Lemma orthonormal_span phi :
phi \in <<S>>%VS ->
{z | z = fun xi => '[phi, xi] & phi = \sum_(xi <- S) z xi *: xi}.