Section RcfTarski.
Variable R : rcfType.
Variable n : nat.
Implicit Types (a b c d : 'rV[R]_(n.+1)).
Definition normv (x : 'rV[R]_(n.+1)) : R := Num.sqrt ((x *m x^T) 0 0).

Lemma segment_construction a b c d :
exists e, bet a b e /\ cong b e c d.