For a nonsingular pair of real
symmetric (r.s.) matrices S and T the maximal number m of lin. ind. vectors
simultaneously annihilated by the associated quadratic forms is computed as a
function of the real Jordan normal form of S−1T. Conversely one can deduce which
real Jordan normal form S−1T must have, if a specific m is the maximal
number of such vectors. Furthermore, two new conditions are found that
assure S and T to be simultaneously diagonalizable by a real congruence
transformation.