4.1 Show that the set of equations
has a unique solution if Σ > 0 and infinite many if Σ is singular.
4.2 Show that the set of equations
always has a solution.
4.3 Show that the shape of the isovalue contours of the mean-square error (J(θ)) surface
are ellipses whose axes depend on the eigenstructure of Σ.
4.4 Prove that if the true relation between ...