let v be Vector of V; :: according to BILINEAR:def 26 :: thesis: (- f) . (v,v) = 0. K
thus (- f) . (v,v) = - (f . (v,v)) by Def5
.= - (0. K) by Def27
.= 0. K by RLVECT_1:12 ; :: thesis: verum