A Quadratic Form is positive semidefinite if it is never , but is 0 for some . The Quadratic Form, written in the form , is positive semidefinite Iff every Eigenvalue of is Nonnegative.
See also Indefinite Quadratic Form, Positive Definite Quadratic Form
Gradshteyn, I. S. and Ryzhik, I. M. Tables of Integrals, Series, and Products, 5th ed. San Diego, CA:
Academic Press, p. 1106, 1979.