Example of two closed vector subspaces of $l^{2}$ whose sum is not closed
61316
Sum of closed spaces is not closed
43504
Proving the existence of a complement subspace $U' \subset V$.
144731
Disjoint closed sets in a second countable zero-dimensional space can be separated by a clopen set
150796
Subspace topology and order topology (2)
78654
An example of a norm which can't be generated by an inner product
139988
Counter example for a result of intersection of subspaces
18423
Subspace of Lindelöf space is not Lindelöf: Example
149971
Closed unit disk homeomorphic to $\mathbb{R}^2$?
34798
Example of element of double dual that is not an evaluation map
42774
Examples of involutions on $\mathbb{R}$
91173
Finite-dimensional subspace normed vector space is closed
108740
$C^1[a,b]$ is closed in $C[a,b]$
146143
Question about proof that finite-dimensional subspaces of normed vector spaces are direct summands
141794
Invariant subspaces of specific dimension
115350
An example of a Banach space isomorphic but not isometric to a dual Banach space
81927
Example of closed and bounded in $\mathbb Q$ set that is not compact
122121
Is there a vector space that cannot be an inner product space?