Homework Statement
Show that the quadratic form h(x) = X^t(AA^t)X is greater than or equal to 0 for all x in R^n.
Homework Equations
The Attempt at a Solution
Since (AA^t)^t = (A^t)^t A^t = AA^t, AA^t can (according to the spectral theorem) be diagonalized in an orthonormal eigenvector...