For any \(n\times m\) real matrices \(A\) and \(B\), show the \(\operatorname {Tr}(AB^*)=\operatorname {Tr}(BA^*)\).
Show that \(\lVert A\rVert =\sqrt {\operatorname {Tr}(AA^*)}\) is a norm.
Suppose \(A\) and \(B\) are \(n\times m\) real matrices. Find the orthogonal matrix \(Q\) that
minimizes \(\lVert QA-B\rVert \) using the norm of part c.