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May
13
reviewed No Action Needed If A,B are real symmetric positive definite matrices, then $B^{-1} AB$ is symmetric positive definite.
Apr
27
reviewed No Action Needed What would base $0$ be? How would/could it work?
Apr
19
reviewed No Action Needed Matrix inversion via Levi-Civita symbols
Apr
19
reviewed No Action Needed Draw the parallelogram spanned by the vectors.
Apr
13
accepted Property of Hausdorff spaces
Apr
13
comment Property of Hausdorff spaces
I don't think that the neighborhoods have to be open to satisfy the Hausdorff condition.
Apr
13
comment Property of Hausdorff spaces
Thanks for your comment. As I said to @AsafKaragila, I can now see my mistake. I wanted to prove it that way, but I think it's a dead end. I will do it your way, it is more direct I find.
Apr
13
comment Property of Hausdorff spaces
Yes you are right, now I can see my mistake. Thanks !
Apr
13
asked Property of Hausdorff spaces
Apr
11
reviewed No Action Needed Evaluating arithmetic sum using prime factorization
Apr
5
reviewed No Action Needed $B_1\cap B_2=0$ and $B_1 \cup B_2$ is a basis for $V_1\cup V_2$.
Apr
5
reviewed No Action Needed Iterative (functional) roots of integer functions (functions on $\mathbb{Z}$)
Apr
5
reviewed No Action Needed How many digits does the integer zero have?
Apr
5
reviewed No Action Needed Example that the union of sigma algebra is not an algebra
Mar
21
reviewed No Action Needed Paths and connectivity of graphs
Mar
18
reviewed No Action Needed Keep factoring and concatenating to get a prime?
Mar
16
comment Proving an equivalence between equalities
Thanks for your answer. It is an unusual way of thinking but it gets the job done. And most important, I can use it to prove something rigorously (and not use a Venn's diagram to get convinced)
Mar
15
comment Does the function $f(x)=x$, $x\in (0,1)$ have a maximum and minimum value?
Here is an intuition why there is no maximum nor minimum value : Suppose you find $x \in (0,1)$ such that $f(x)$ is the maximum. Since $(0,1)$ is an open set, for any x, you can find another point right next to it that is greater. Therefore the maximum was not one and therefore there exist none.
Mar
15
reviewed Reviewed Discrete Math - Logic - Implication Problem
Mar
15
comment Discrete Math - Logic - Implication Problem
Don't write in uppercase, it looks like you are yelling