$p$ and $q$ orthogonal projections in $B(H)$, then the orthogonal projection onto the intersection space is the strong operator limit of $(pq)^n$
71350
Let $H$ be a Hilbert space with projections $P,Q$, then $\lim_{n\to\infty}(PQ)^nx= Rx$ for all $x\in H$, where $R$ is the projection to $PH\cap QH$
20467
Show that $(y_n)\in l^q$
144019
A strictly positive operator is invertible
69497
Show that the set of all $n \times n$ orthogonal matrices, $O(n)$, is a compact subset of $\mbox{GL} (n,\mathbb R)$
57609
Hahn-Banach proof by extension of basis
138825
The strong topology on $U(\mathcal H)$ is metrisable
125277
Image of the tensor product of strict maps of Banach spaces
119775
Density of finite rank operator in compact operators on Hilbert spaces
104607
Hahn-Banach theorem, dual space
18205
Orthogonal Projection
114524
Proof Verification: the orthogonal complement of the column space is the left nullspace
59477
Density of orthogonal matrices with rational coefficients
146839
Orthogonal Projection onto the $ {L}_{\infty} $ Unit Ball
19946
Let $W$ be a given subspace of $V$ find the orthogonal complement $W^{\perp}$
154762
Dual space of a finite dimensional normed space
14084
The Multiplier Algebra of the Hardy Hilbert Space
103045
Composition of Proximal Operators