Solution
= Solution
The <conjugate transpose> reverses the order of <matrix multiplication>. Since $A$ and $B$ are <Hermitian matrices>,
$$
(AB)^\dagger=B^\dagger A^\dagger=BA.
$$
Consequently $\boxed{AB\text{ is Hermitian}\ \Longleftrightarrow\ AB=BA}$: the condition is exactly that the two <matrices> <commute>.