How can I formally demonstrate this relations with hermitian operators?(A^{\dagger})^{\dagger}=A
(AB)^{\dagger}=B^{\dagger}A^{\dagger}
\langle x|A^{\dagger}y \rangle=\langle y|Ax \rangle ^*
If \ A \ is \ hermitian \ and \ invertible, \ then \ A^{-1} \ is \ hermitian
I've tried to prove them...