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3h
answered If an $n\times n$ matrix $A$ is diagonalizable and has only one eigenvalue $\lambda$ with multiplicity $n$, then $A = \lambda I$. True or False?
7h
comment How to prove the following identity?
Crossposted on MO.
8h
comment Is every point in the set defining some curve or line in $\mathbb{C}$ or $\mathbb{R}$ a boundary point?
@RobArthan: My answer addresses the question that was initially asked. The OP edited the question an hour ago and added the simple hypothesis; note that my answer was submitted well before that.
9h
comment Taking the derivative of a matrix multiplied by a vector
In your definition, do you mean an $m\times n$ matrix?
10h
comment Write the vector field such that its integral curves are the meridians of $S^2$
Note that \cos produces $\cos$ as opposed to cos which produces $cos$.
10h
revised Figure out attendance needed for remaining days to reach attendance goal
edited tags
10h
comment Taking the derivative of a matrix multiplied by a vector
What definition of derivative are you using?
16h
awarded  Enlightened
22h
awarded  Revival
22h
reviewed Close Real Analysis Differentiating under the integral
22h
reviewed Close linear algebra: deciding if this is a vector space over R?
23h
revised Find a $4\times 4$ matrix whose reduced row echelon form has two leading ones and whose row space intersects its column space only at the origin.
edited tags
1d
awarded  Good Answer
1d
awarded  Good Answer
1d
revised Do two closed subsets of $[0, 1]$ with measure $\frac{1}{2}$ intersect?
rolled back to a previous revision
1d
comment Are there rings whose multiplicative identity is not the number 1 or number 1-based?
@GerryMyerson: The example is the same, but we answered only minutes apart.
1d
comment Functional equation and algebra
This should be a comment on Yiorgos S. Smyrlis' answer, not a separate question.
1d
revised Riemann integrable proof?
added 98 characters in body
1d
comment Riemann integrable proof?
Welcome to math.SE: since you are new, I wanted to let you know a few things about the site. In order to get the best possible answers, it is helpful if you say in what context you encountered the problem, and what your thoughts on it are; this will prevent people from telling you things you already know, and help them give their answers at the right level.
1d
awarded  Nice Answer