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2h
revised How many continuous involutions on $\mathbb R$ are there?
added 65 characters in body
2h
answered How many continuous involutions on $\mathbb R$ are there?
2h
comment How many continuous involutions on $\mathbb R$ are there?
What are the conditions on $f$? For example, does $f$ need to be continuous?
10h
answered For a matrix $O$ containing columns which are an orthonormal basis for a column space, why does $O^{\prime}O = I$?
10h
comment Show $\lim_{n\to\infty}(Lu_n) = L(\lim_{n\to\infty} u_n)$
Your new proof is also completely fine.
10h
comment Show $\lim_{n\to\infty}(Lu_n) = L(\lim_{n\to\infty} u_n)$
The fact that you write $\lim_{n\to\infty}\|Lu_n-Lu\|$ assumes that this limit exists before you've actually proven that the limit is zero. The proof would make sense if you instead wrote $$ \limsup_{n\to\infty}\|Lu_n-Lu\|=\limsup_{n\to\infty}\|L(u_n-u)\|\leq \lim_{n\to\infty}M||u_n-u||=0 $$
10h
revised Suppose $AB=BA$ and $A^{1965}=B^{2015}=I$. Prove that $A+B+I $ is invertible.
edited tags
11h
comment Suppose $AB=BA$ and $A^{1965}=B^{2015}=I$. Prove that $A+B+I $ is invertible.
It is significant that $2015$ is not a multiple of $3$.
May
22
revised Necessary condition for existence of a positive solution of a linear system
edited tags
May
22
answered convert the inverse of sum of two hermitian matrices into sum of two or more matrices.
May
22
comment Orthogonal complex matrices: polar decomposition
It's not a decomposition in the sense of the Cartesian product of spaces. However, like the polar decomposition of $\Bbb R^n$, it is a Cartan decomposition.
May
21
comment free tool for algebraic manipulations of commutator expressions
(That's symbolic python). You can download Python and the various packages that go along for free
May
21
comment free tool for algebraic manipulations of commutator expressions
The SymPy quantum mechanics package handles commutators beautifully
May
21
revised Orthogonal complex matrices: polar decomposition
edited tags
May
21
answered Orthogonal complex matrices: polar decomposition
May
21
revised Rotation Matrix and programming
edited tags
May
21
revised Matrix of Killing form a Lie algebra
added 56 characters in body
May
21
answered Matrix of Killing form a Lie algebra
May
21
revised Is there a name or symbol for the matrix division resulting in a scalar?
edited tags
May
21
comment linear map as a product of certain linear maps
Any invertible map can be written as the product of such maps