4. Let H be a Hilbert space. For any subset ACH (not only subspaces) we can define A = {t G H | Vu€ A: lu}. a (a) Show t
Posted: Mon May 09, 2022 11:45 am
4. Let H be a Hilbert space. For any subset ACH (not only subspaces) we can define A = {t G H | Vu€ A: lu}. a (a) Show that A is a closed subspace of H. (b) Show that At = span(A)+, where span(A) C H denotes the linear span of A. (c) Let U CH be a subspace. Show that (Ut) is the closure of U. 5