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May
10
revised Verify that the set $\Omega = \lbrace (u,v) \in \mathbb{R}^2 \mid |u| + |v| \leq 1 \rbrace$ is Jordan measurable
added 16 characters in body
May
10
awarded  Good Answer
May
10
answered Verify that the set $\Omega = \lbrace (u,v) \in \mathbb{R}^2 \mid |u| + |v| \leq 1 \rbrace$ is Jordan measurable
May
10
comment When should matrices have units of measurement?
I'm sure your fraction field construction is mathematically sound, but it creates a lot of junk which is not actually there. It's similar to nonstandard analysis, which automatically gives birth to more orders of infinity than there are atoms in the universe, and still allows adding and multiplying any finite number of objects so created. – In my view the set of all lengths, say, is not $={\mathbb R}$, but a one-dimensional vector space over ${\mathbb R}$.
May
10
answered Find all $\alpha$ such that for any $x>-1$ we have $\ln(1+x)\leq x-\frac{x^2}{2}+\alpha x^3$
May
10
revised How many $n-$digit number that contain only digits $ 1,2,3,4,5,6$
added 150 characters in body
May
10
revised Find XY given matrix YX where X is a row matrix and Y is a column matrix
edited title
May
10
revised Metrics on the set of natural numbers
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May
10
revised How many $n-$digit number that contain only digits $ 1,2,3,4,5,6$
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May
10
comment Is there such an integer?
Yes, it's possible: Let $a_n=2$ for all $n$, and $b_n=1$ for all $n$. Then $b_n=1 ({\rm mod}\> a_n)$ for all $n$.
May
10
answered How many $n-$digit number that contain only digits $ 1,2,3,4,5,6$
May
9
awarded  Nice Answer
May
9
answered Is there any way to define arithmetical multiplication as other thing than repeated addition?
May
9
comment I have a ball that intersects a cylinder and I need the volume. How do I do it?
Your definition of the cylinder doesn't make sense.
May
9
revised Diffeomorphism ( differential geometry)
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May
9
revised No continuous injective map $f: \mathbb{S}^1 \to \mathbb{R}$
added 322 characters in body
May
9
comment Describe the image of the set $\{z:|z|<1, Im(z)>0\}$ under the mapping $w =\frac{2z-i}{2+iz}$
@Sara: That is correct.
May
9
revised Prove or disprove that EigenVectors of $A^T$ are the same of $A$.
added 5 characters in body
May
9
answered Prove or disprove that EigenVectors of $A^T$ are the same of $A$.
May
9
answered Diffeomorphism ( differential geometry)