consider v being Vector of V, w being Vector of W such that
A1: f . v,w <> 0. K by Th41;
reconsider B = w + (RKer f) as Vector of (VectQuot W,(RKer f)) by VECTSP10:24;
reconsider A = v + (LKer f) as Vector of (VectQuot V,(LKer f)) by VECTSP10:24;
(QForm f) . A,B = f . v,w by Def23;
hence not QForm f is constant by A1, Th41; :: thesis: verum